Privacy 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.

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 containing information such as your IP address, the time of the request and user-agent (UA) information about your browser and device are generated as part of Cloudflare’s CDN operations.

These are infrastructure logs processed by the hosting provider, Cloudflare. Separately, semku collects and retains anonymous usage statistics, 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.

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 anonymous usage statistics, 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.

Our own usage statistics and error reports are sent only from Korean, Japanese and English pages. 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. 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, do not send our own usage statistics or error reports and only accept 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.

Usage statistics include stages of use, such as starting an attempt, displaying results, copying or requesting printing, the time they occur, and fixed identifiers distinguishing pages and features. 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. Raw inputs, clipboard contents, full URLs and search terms are also excluded. Recording the connecting country and state/province, the referral source (site address and page path) and the display language is explained separately in §4-2.

Attempts and sessions are distinguished by randomly generated UUIDs. In the browser, these identifiers are held only in memory and are not saved persistently in cookies or browser storage. Measurement does not use cookies or identify users by device fingerprinting. The transmitted identifiers distinguish usage statistics and error records. 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.

Error reports include the error type, code and time and, where available, a registered program-source identifier and line and column positions. Raw error messages and full stack traces are not sent. Usage statistics and error reports also include the site, deployment version and a random record identifier. Recording connection records (IP addresses), browser signals (User-Agent Client Hints) and the display language is explained in §4-2. Hosting access logs are explained separately in §2.

The on-screen “Send feedback” widget submits only the rating (👍·👎) you select and the text you write when you press “Submit”. A random ID distinguishing the submission, the page, site, deployment version and type of inquiry are also sent. There are no fields for personal data such as your name, email address or phone number, and calculator inputs or results are not attached automatically. Whatever you write and submit in the free-text field is sent as is, so please do not enter personal data, passwords, authentication keys or payment details.

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 only for visits to Korean, Japanese and English pages that send usage statistics. These items are not recorded for visits to German or Spanish pages or for feedback submissions, and are not included in error reports. Standard hosting access logs are separate from these records and are explained in §2. To improve the service, we record the country and state/province-level region at the time of your visit (an estimate based on the connecting network), which site you came from, and one display-language setting reported by your browser (for example, ko-KR). Location is recorded only at country and state/province level; no city or precise location is recorded. Connection records, including IP addresses, are automatically generated when you use the service and are retained to operate the service securely and identify abnormal access. Cloudflare is the data processor for this site. Collection of this item is enabled only after this notice is published; it is not collected retrospectively for use before collection is enabled.

For the referral source, we record the address of the immediately preceding site and the page path within it. Query information appended to an address, such as search terms, is not recorded. Even if you arrive through a search, the search terms you entered are not saved. For the display language, we do not record the full list of preferred languages or the raw request headers sent by your browser.

To identify bots, we may collect and use signals your browser reports about its type and version, along with an indication of whether automation tools are being used. These browser signals are estimates; they do not conclusively identify the browser’s type or version or whether automation tools are being used. Collection of this item is currently disabled and will only be enabled after this notice is published. It is not collected retrospectively for use before collection is enabled. The raw user-agent (UA) request header is not saved in these records.

The records in this section are kept per visit only, with no identifier linking one visit to another.

The following recording start dates apply only to visits to Korean, Japanese and English pages that send usage statistics. The records in this section begin with visits after this notice is published and do not apply retrospectively to earlier visits. The connection region and referral source have been recorded since 2026-09-20, and the display language since 2026-09-24. Browser signals are not yet recorded as of this revision. When recording begins, we will state the start date here in this section.

5. Inquiries and corrections

Please send questions about personal data processing or requests to correct the facts in this policy to contact@semku.com.

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.

5-1. Limitation of liability

The tools and results on this site are provided as is, without any guarantee of accuracy or completeness. Do not use them as the basis for important decisions, including tax, financial, medical or legal decisions. We accept no liability for damage arising from their use. By using the service, you are deemed to agree to this.

6. Policy information

Version: v4.12
Effective date: 2026-09-30
Operated by: Dan Kim
Contact: contact@semku.com
Revision history: v2 — Added information on browser local storage and the handling of sharing links on /dday/ko.
v3 — Clarified the differences in information processing for ordinary calculations, browser storage, and the use of date-transfer and sharing links.
v3 → v4 — Reflected the collection of our own usage statistics and clarified the scope of processing for error reports and feedback.
v4 → v4.1 — Clarified the information included in date-transfer links from the Suneung countdown and what is transmitted when those links are opened.
v4.1 → v4.2 — Reflected browser local storage and deletion methods for notes and personal days off in the Japanese calendars, and clarified the scope of our own usage statistics and error reports for the Japanese calendars and the /calendar/ja guide page.
v4.2 → v4.3 — Updated the paths in this document to reflect the URL restructuring (all pages use the /서비스/언어 path). No changes to the items collected.
v4.3 → v4.4 — As more language editions of the yearly calendars became available, updated the list of page paths that save notes and personal days off in the browser to match the pages actually published. No changes to the items collected or processing methods.
v4.4 → v4.5 — Added “5-1. Limitation of liability” (notice that results are for reference and accuracy is not guaranteed). No changes to the items collected.
v4.5 → v4.6 — Added “4-2. Connection region and referral source” (advance notice of plans to record the connecting country, state/province and referring host; notice precedes collection, with no recording as of the revision date). Moved these two categories from the collection description in §4-1 to §4-2.
v4.6 → v4.7 — Added the operator (Operated by: Dan Kim) to the policy information. Consolidated the one-line disclaimer previously displayed at the bottom of every page into “5-1. Limitation of liability” in this policy and removed it from those displays. No changes to the items collected or processing methods.
v4.7 → v4.8 — Added display language (browser language setting) to “4-2. Connection region and referral source” (advance notice of planned recording; notice precedes collection, with no recording as of the revision date). The full list of preferred languages and the raw request headers sent by the browser are not recorded.
v4.8 → v4.9 — Added advance notice of plans to record browser type and version signals (User-Agent Client Hints) to “4-2”, and specified that the connection region is an estimate and collection is not retrospective. Consolidated the user-agent (UA) wording in §4-1 into a reference to §4-2. No recording as of this revision (notice precedes collection).
v4.9 → v4.10 — Corrected the current-status wording in “4-2” to reflect the actual state: the connection region and referral source have been recorded since 2026-09-20, and the statement “not yet recorded” in v4.9 was an error (display language and browser signals remained unrecorded). No changes to the items collected or processing methods.
v4.10 → v4.11 — Added the start date for recording the display language (2026-09-24) to “4-2” and removed the remaining statement in that section that “the display language is not yet recorded”. Browser signals remain unrecorded. No changes to the items collected or processing methods.
v4.11 → v4.12 — Corrected the language-specific scope of our own usage statistics, error reports and records of connection region, referral source, display language and IP address; browser storage on the five D-day pages and nine yearly calendar pages; and the description of transmission for date-transfer fragments and sharing-link query strings. No changes to the items collected or processing methods.