Methodology

Exam countdown: every formula

This is the trust contract behind the exam countdown planner — how days-left is computed, how prep estimates work, what the reminders can and can’t do, and the timezone guarantees. If you can’t hand-verify a number from this page, the tool shouldn’t show it.

Days left — the timezone guarantee

Days left = (exam calendar date) − (today’s calendar date), as whole days. The computation never touches timestamps:

  1. Both dates are parsed as local calendar dates — never via new Date("YYYY-MM-DD"), which JavaScript interprets as UTC midnight and shifts the day for anyone west of UTC.
  2. The difference is computed on UTC-normalized day boundaries (integer day math), so daylight-saving transitions — 23-hour and 25-hour days — cannot add or remove a day.
  3. “Today” is re-read from the device on every load and whenever the tab regains focus, so a countdown never goes stale overnight.

The guarantee: a student in Kathmandu (+5:45) and one in New York (−5:00) see the same “days left” for the same exam date on the same local calendar day. This is covered by an automated test matrix spanning UTC−11 to UTC+14, both US daylight-saving transitions, and the international date line. Exam dates must be real calendar dates (30 February is rejected, not rolled over) between the years 2000 and 2100.

Prep estimates

When an exam is linked to a subject in the syllabus tracker — by an explicit link, or automatically when the names match — each card shows a daily target:

Required topics/day = topics remaining (not marked confident) ÷ days left, to one decimal.

If you entered available study hours, they’re shown alongside as context — the tool does not pretend to know how long your topics take. Special cases: past exams say so; a fully-covered syllabus says “use the time for revision”; an exam today skips the math and says focus on the weakest topics; a subject with no topics yet asks you to add them first. Honest limitation: the estimate assumes topics take roughly equal effort.

Reminders — what they are and aren’t

Every time the page loads, exams due within the next 7 days (including today) produce a “Coming up” banner: “Physics final is in 3 days”, “Chemistry is tomorrow”, “Maths is today”. That’s the whole reminder system — deliberately. A static page with no backend cannot schedule push notifications or wake itself up; any countdown app that claims otherwise is either running a server or misleading you. The banner recomputes on load and on day change, so it’s always current when you open the page.

Storage and privacy

Your exams are stored as a single document in your browser’s local database (IndexedDB, with an in-memory fallback if your browser blocks storage). Linked tracker subjects keep their exam date in sync through a stored exam reference; deleting a countdown keeps the subject’s date (it’s still meaningful) but clears the link. Nothing is uploaded, there are no accounts, and clearing your browser data will delete your countdowns.

Details of data handling for all tools are in the privacy policy.