semkuPrivacy policy
1. Service and processing principles
semku is a free calculator that you can use without signing up, logging in or making a payment. It does not sell goods or services.
Tool descriptions are written with AI assistance, and the site operator reviews them and takes responsibility for their content.
All calculations run in your browser. Dates, amounts and quantities entered for ordinary calculations are not sent to the server. Schedules you save on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es, and notes and personal days off you save in the yearly calendars, are kept in the browser on your device.
Links on /naljja/ko or /suneung-dday/ko that pass a date to the D-day calculator put the date and transfer-source marker in the URL fragment (#d=…). This part is not sent to the hosting server as part of the request address, even when the link is opened. Sharing links created by users on the five D-day pages (/dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es) include the target date in the query string (?d=…), and include the schedule name only if the user chooses to add it (?d=…&n=…). Creating or copying a link does not in itself send this information to the server, but opening a sharing link to visit semku sends the information in its query string to the hosting server as part of the request address. §3-1 explains links and access logs in more detail.
2. Server access logs
semku is served as a static site on Cloudflare Pages. When you visit the site, standard access logs are generated as part of Cloudflare’s CDN operations.
These are infrastructure logs processed by the hosting provider, Cloudflare. Separately, semku collects and retains our own usage records, error reports and feedback submitted directly by users through its own endpoints on semku.com, for the operator to analyze usage and improve the service. The scope of collection is explained in §4-1.
Cloudflare, Inc. (USA) is our processor for hosting, transmission, temporary storage in our own collection path and administration access. It processes connection information such as IP addresses, access times and user agents to serve the site. If you email us, Google processes the correspondence and sender address as our email service provider. GitHub retains backup copies of some usage, error and feedback data from 11–16 September 2026; those copies contain no IP addresses.
Collected records are also processed on the operator's computer in Korea, and backup copies are kept on that computer and its backup device. Cloudflare processes requests across its global infrastructure, and our collection buffer is configured in Asia-Pacific, so processing is not limited to the EEA.
For transfers outside the EEA, transfers to the United States through Cloudflare, GitHub (backup copies from 11–16 September 2026) and Google (email received) rely on the EU–US Data Privacy Framework (DPF) adequacy decision (EU) 2023/1795 (with Cloudflare's restricted transfers not covered by the DPF using the Standard Contractual Clauses (SCCs, Decision (EU) 2021/914, Module 2) under its Data Processing Addendum (DPA)), and transfers to the operator's computer in South Korea rely on the EU adequacy decision for the Republic of Korea (EU) 2022/254; copies of the relevant documents are available at https://www.dataprivacyframework.gov/list or by request to the email above.
Our hosting provider Cloudflare, Inc. (USA) instructs your browser through a response header to report network errors (NEL), and supporting browsers keep that instruction for seven days. If a connection to this site fails, the browser sends the failed page address, the previous page address (referrer), the error type, the response status code, the server IP address, the protocol, the elapsed time and the browser information (user agent) to Cloudflare's reporting endpoint (a.nel.cloudflare.com), and your IP address reaches Cloudflare with the report. Cloudflare uses these reports to find and fix network connection problems; successful connections are not reported, and the reports are separate from our own usage statistics.
Transfers abroad: to perform our agreement with you to provide the free tools, we entrust processing and storage abroad (Personal Information Protection Act of Korea, Article 28-8(1)(3)), transferring access IP, access time, user agent and requested URL, usage, error, feedback and automated-request records and network error reports over the network to Cloudflare, Inc. (a US company, privacyquestions@cloudflare.com) each time you access the site or a record or report is sent; processing takes place in Cloudflare's data centres worldwide, nearest to where you connect, and our record buffer is configured in Asia-Pacific. Cloudflare uses them for hosting, delivery, temporary storage of records and identifying connection problems, deletes its copy of received usage, error and feedback records once they are moved to our operational store, keeps automated-request records in its storage without a set period, and keeps connection information and network error reports for the period set in Cloudflare's privacy policy (https://www.cloudflare.com/privacypolicy/). If you email us, the message and sender address are transferred over the network at that time to Google LLC (a US company, https://support.google.com/policies?p=privpol_privts), to which we entrust email processing, used in Google's data centres worldwide to provide the email service and kept until the operator deletes them. Blocking the measurement script stops the transfer of usage and error records (the tools still work), browsers that do not support network error reporting send no such reports, not emailing avoids the transfer to Google, and refusing Cloudflare's processing needed to reach the site means the site cannot be used.
Transfer of GitHub backup copies abroad: some usage records (event type, properties, time, page identifier and session number), error records (error type, code, location, response status, time, page identifier and session number) and feedback (type, text, reply email address if given and page identifier) received on 11–16 September 2026 were transferred over the network to GitHub, Inc. (USA, privacy@github.com) when they were backed up during that period; these copies contain no IP addresses. GitHub uses them to store the backup, and the copies are kept until the operator deletes them. You can ask us at the contact above to refuse this transfer or have the copies deleted, and refusing does not affect your use of the site.
3. Cookies and browser storage
semku currently sets no cookies of its own.
When you save a schedule on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es, its name (if entered) and target date are saved in the browser’s local storage (localStorage) on your device. Saving does not send this information to the server, and semku cannot view the list saved in your browser. semku does not synchronize saved schedules across browsers or devices or back them up separately. Clearing your browser data also removes your saved schedules.
When you save notes or personal days off on /calendar-2026/ja, /calendar-2027/ja, /dallyeok-2026/ko, /dallyeok-2027/ko, /kalender-2026/de, /kalender-2027/de, /calendario-2026/es, /calendar-2026/en or /calendar-2027/en, the selected dates, notes entered for those dates and personal-day-off settings are saved by year in the browser’s local storage (localStorage) on your device. Saving does not send this information to the server or include it in the URL, and semku cannot view the content saved in your browser. semku does not synchronize saved notes or personal days off across browsers or devices or back them up separately. Clearing your browser data also removes the saved content.
You can delete saved schedules individually from the saved list on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es, or remove them by clearing your browser data. You can delete notes and personal days off saved in a yearly calendar by date on that year’s page, delete all saved content for that year, or remove it by clearing your browser data. Deleting all content for a year removes only that year’s notes and personal days off; it does not delete content for other years or schedules saved on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es.
The pages that use the browser’s local storage are the five D-day pages (/dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es), which save schedule lists, and the nine yearly calendar pages (/calendar-2026/ja, /calendar-2027/ja, /dallyeok-2026/ko, /dallyeok-2027/ko, /kalender-2026/de, /kalender-2027/de, /calendario-2026/es, /calendar-2026/en and /calendar-2027/en), which save notes and personal days off. Other calculators do not save inputs in the browser’s local storage. If you use links that include dates or names, §3-1 applies. The yearly calendars have no feature for including selected dates, notes or personal-day-off settings in links.
4. Advertising and analytics tools
There are currently no advertisements, advertising scripts or requests to advertising networks. We do not use third-party visitor analytics services, including GA4. We do use semku’s own measurement system; its scope of collection and purpose are explained in §4-1.
We do not insert visitor analytics scripts to verify site ownership for Google Search Console. If we introduce advertising or change our analytics methods or the items we collect, we will revise this policy to match actual behavior and apply any necessary consent procedures.
4-1. Our own usage statistics, error reports and feedback
semku collects and retains our own usage records, error reports and feedback submitted directly by users so that the operator can analyze usage and improve the service. This information is sent to our own endpoints under semku.com/api/telemetry/v1/ and is not used for advertising or third-party tracking.
The processing described in this section also applies to the yearly calendars /calendar-2026/ja, /calendar-2027/ja, /dallyeok-2026/ko, /dallyeok-2027/ko, /calendar-2026/en and /calendar-2027/en and the guide pages /calendar/ja, /dallyeok/ko and /calendar/en. The same processing applies to German and Spanish pages, including the yearly calendars and guide pages /kalender-2026/de, /kalender-2027/de, /calendario-2026/es, /kalender/de and /calendario/es. Until immediately before collection began on 12 October 2026 (Korean time), these pages did not send our own usage statistics or error reports and only accepted feedback submissions. Fixed identifiers distinguish pages and features. Selected dates, notes and personal-day-off settings are not sent in usage statistics or error reports.
To understand and improve features and language versions, we record page arrivals, interaction starts, ways of obtaining results and departure times for sessions already started. Records also contain times, page, feature and build identifiers, temporary session and operation numbers, estimated country and state or province, referral sources, one browser display-language setting, and device type (phone, tablet or PC) and screen-size band.
Dates, amounts, quantities and schedule names entered in calculators, calculation results, and dates, notes and personal-day-off settings selected in yearly calendars are not sent in usage statistics or error reports. These values are not sent as hashes or grouped into ranges of length, amount or other values either.
Saving schedules on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es and notes and personal days off in yearly calendars uses the browser’s local storage described in §3, separately from these measurement identifiers.
To investigate and fix technical faults, we record error type, code and time, page and build identifiers and a temporary session number.
Browser errors also record estimated country and state or province, one display-language setting and the referring hostname.
Usage statistics and error reports also include the site, deployment version and a random record identifier. Hosting access logs are explained separately in §2.
The on-screen “Send feedback” widget submits your feedback only when you press “Submit”. A random ID distinguishing the submission, site, deployment version and type of inquiry are also sent. Calculator inputs or results are not attached automatically.
When you submit feedback, we receive your text, chosen rating and the relevant page identifier. The form has no reply-address field and cannot provide individual replies, so send rights requests needing a reply to the email above.
When the collection server classifies a request’s country as being in the European Economic Area (EEA), or cannot determine its country, we collect our own usage analytics and error reports for that request only if you allow performance cookies in the cookie settings banner; before you choose, or if you reject them, we do not collect them, and new collection of feedback remains blocked. You can change this choice at any time via “Cookie settings” at the bottom of the page. If you visit from the United Kingdom, you can turn off usage analytics and error reports via “Turn off statistics” at the bottom of the page.
To understand AI-agent access, we separately record the user-agent string, service category, path without query parameters, time, and available network and verification information only for requests matching a defined automated-service list and a document-path condition, without storing raw IP addresses, cookies or request bodies.
4-2. Connection region, referral source and browser signals
The country, state/province, referral source, display language and IP address records in this section are created for visits to Korean, Japanese, English, German and Spanish pages that send usage statistics. These items were not recorded for visits to German or Spanish pages until immediately before collection began on 12 October 2026 (Korean time). These items are not recorded for feedback submissions. Standard hosting access logs are separate from these records and are explained in §2.
Usage records include the full IP address.
We record the referring site's hostname and the page path supplied for external referrals, excluding query strings and fragments.
We keep raw IP addresses unchanged for as long as we operate the service, for security and abuse prevention (looking up and comparing the same IP in the administration view); for statistics we also record, alongside them, the IP address minus its last part and a pseudonymous value made with a secret key (which links visits from the same address). We keep referring page paths as they are; only secret values in a path, such as passwords, Wi-Fi passwords, two-factor authentication secrets and login tokens, are removed the next day. We keep feedback as written, including email addresses and phone numbers, to reply and to follow up on the same enquiry; only numbers in the form of a Korean resident registration number are removed the day after we finish handling it. Visits by bots and automation tools are also recorded, marked separately from human visits.
Together with the IP and referral page path kept as described above, records include fields such as event and page identifiers, session numbers, times, country, region, referring hostname and display language. We continue to treat these as personal data. We use aggregate results for statistics and keep individual records without an end date (for as long as we operate the service) to recalculate statistics and improve the service, viewing them through an access-restricted administration interface. Error, feedback and automated-request records are also kept without an end date (for as long as we operate the service).
To keep personal data secure, only the operator views individual records, in an admin screen that requires operator authentication and on the operator's computer; raw IP addresses and backup copies are likewise kept where only the operator can access them.
5. Inquiries and corrections
The controller for the personal data processing described in this notice on semku is Dan Kim, the individual operator (“the operator” in this notice). You can send privacy enquiries and rights requests through the site's feedback button or email the operator's shared contact address, agt.tije@gmail.com; use email if you need a reply.
For its calculation and link features, semku does not retain calculator inputs or date-transfer and sharing links in separate server records or databases. Content that users write and submit as feedback is collected and retained as described in §4-1. semku cannot view, correct or delete on your behalf schedules saved in your browser on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es, or notes and personal days off saved in yearly calendars. You can delete saved schedules yourself from the saved list on /dday/ko, /days-until-calculator/en, /ato-nannichi/ja, /tage-zaehler/de and /contador-de-dias/es, and notes and personal days off on the relevant yearly calendar page, or remove them by clearing your browser data.
Cloudflare access logs that may be generated when a link is opened are separate from these lists saved in your browser and are explained in §2 and §3-1.
Where GDPR applies, the basis for usage statistics, excluding operator visits, fixing errors, responding to general feedback and email, hosting, request limits, automated-request analysis and investigating technical problems is our legitimate interest in each stated purpose (Article 6(1)(f)). Processing necessary to handle data protection rights requests is based on compliance with legal obligations (Article 6(1)(c)).
Subject to legal conditions, you can request access, rectification, erasure and restriction of processing.
Right to object
You may object at any time, on grounds relating to your particular situation, to processing of your personal data under Article 6(1)(f) GDPR. We will stop that processing unless we demonstrate compelling legitimate grounds overriding your interests, rights and freedoms, or the processing serves the establishment, exercise or defence of legal claims.
You may lodge a complaint with a supervisory authority, particularly in the Member State of your habitual residence, workplace or the alleged infringement (Article 77 GDPR).
You have no statutory or contractual obligation to submit feedback or enable transmission of usage data; the tools work without feedback and with the measurement script blocked. We make no solely automated decisions producing legal or similarly significant effects on you, and possible-bot labels in administration are for internal analysis and do not trigger action against users.
6. Policy information
- Version
- v5
- Effective date
- 2026-11-03
- Operated by
- Dan Kim
- Contact
- agt.tije@gmail.com