Date Difference Calculator
How many days until the deadline? How long since the semester started? Pick two dates and get the exact difference in days, weeks, approximate months and years, plus the total in hours and minutes. Day math is DST-safe — it's computed on calendar dates, not raw time.
Time until end date
30 days
- Days
- 30 days
- Weeks
- 4 weeks
- Months (approx)
- 0 months
- Hours
- 720 hours
Day counts are calendar-accurate (leap years included) and DST-safe. Months/years are approximations (≈ 30.44 days / 365.25 days).
How it works
- Pick a start date and an end date.
- The calculator counts whole days between them (calendar days).
- Weeks, approximate months and years are derived from the day count.
- Total hours and minutes are shown for exact durations (e.g., an internship length).
- Dates can be in either order — the result correctly reports past or future.
The formula
Days between dates
days = round((UTC(end) − UTC(start)) ÷ 86 400 000)
Both dates are normalized to UTC midnight, so daylight-saving shifts never skew the count.
Worked example
Worked example
- Semester starts September 1, 2026; finals end December 18, 2026
- days = 108; weeks = 15
The semester is 108 days (≈ 15 weeks 3 days) — about 15.4 weeks of teaching and exams.
Common mistakes
- Assuming a “month” has a fixed length — the calculator reports months as an approximation (~30.44 days) and days as the exact figure.
- Off-by-one on inclusive dates — “between today and tomorrow” is 1 day.
- Ignoring that some systems count the end date as a full day — check the context you need.
Frequently asked questions
Is the day count inclusive or exclusive?
It counts the number of whole days between the two calendar dates. For “days until” phrasing (like a deadline), this matches expectations: today to tomorrow = 1 day.
Does it handle leap years?
Yes — the calculation uses real calendar dates, so February 29 is handled correctly in leap years.
Can I calculate business days?
Not yet — weekday filtering is planned. The current tool reports calendar days.
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