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Weeks between dates calculator

A weeks between dates calculator divides the number of calendar days separating two dates by seven. Between 1 January 2026 and 25 December 2026 there are 358 days, which is 51.14 weeks — 51 whole weeks and 1 day. That same span covers 25 complete fortnights and 51 full Saturday–Sunday weekends.

Calculated in your browser — nothing is uploaded.

Result

Weeks between the two dates

51.14 weeks

weeks = (end − start in days) ÷ 7

Whole weeks and days
51 w 1 d
Fortnights
25.57
Full weekends
51
Weekdays
256
Working weeks (5-day)
51.2
Total days
358

There are 51.14 weeks between January 1, 2026 and December 25, 2026 — 51 whole weeks and 1 day, or 358 days in total. That span covers 25 complete fortnights and 51 full weekends.

How to use the weeks between dates calculator

  1. 01

    Enter the start date

    Type or pick the earlier date. The order does not matter — the calculator returns the same span whichever way round the two dates are entered.

  2. 02

    Enter the end date

    Type or pick the later date. The start date counts as day zero, so add one day to the end date if both endpoints should be included.

  3. 03

    Read the week count

    The result strip shows the span in weeks to two decimal places. The row beneath restates it as whole weeks plus leftover days, which is the form most people want.

  4. 04

    Check the other units

    The remaining rows give fortnights, complete weekends, weekdays and five-day working weeks for the same interval, so a payroll or project span needs no second calculation.

The formula

weeks = days ÷ 7
whole weeks = ⌊days ÷ 7⌋,   remainder = days mod 7
fortnights = days ÷ 14
days
Calendar days between the two dates, counting the start date as day zero.
weeks
The span in weeks including the fractional part, such as 51.14.
whole weeks
The number of complete seven-day weeks, discarding any part week.
remainder
Days left over after the whole weeks, always between 0 and 6.
fortnights
The span in fourteen-day blocks, the unit used by fortnightly payroll.

Weekday, weekend and fortnight counts all use whole-week arithmetic rather than a loop over every date: each complete seven-day block contributes exactly one of each weekday, so only the remaining 0–6 days need examining individually. A span of a century therefore costs the same to compute as a span of a week. Every calculation runs in UTC, which avoids daylight-saving transitions — without that, two days a year are 23 or 25 hours long and a naive division by seven drifts.

Worked example

Start date
1 January 2026
End date
25 December 2026
Result
51.14 weeks

The interval spans 358 calendar days. Dividing by seven gives 51.142857, which displays as 51.14 weeks. Taking the whole part gives 51 complete weeks, and 358 − (51 × 7) = 1 leaves a remainder of one day, so the span is 51 weeks and 1 day. Dividing the same 358 days by fourteen gives 25.57 fortnights, or 25 complete fortnights with 8 days left over. The span contains 256 weekdays, which at five weekdays per working week is 51.2 working weeks.

Frequently asked questions

How many weeks are between two dates?

Divide the number of calendar days between the two dates by seven. From 1 January 2026 to 25 December 2026 is 358 days, and 358 ÷ 7 = 51.14 weeks. Expressed without a decimal that is 51 whole weeks and 1 remaining day. The fractional form suits averages and rates; the whole-weeks-plus-days form suits schedules and deadlines.

What is the difference between whole weeks and decimal weeks?

Decimal weeks keep the part week as a fraction, so 358 days becomes 51.14 weeks. Whole weeks discard the fraction and report the leftover separately, giving 51 weeks and 1 day. Use the decimal form when dividing a total by the span — a weekly average or burn rate — and the whole form when counting out actual calendar weeks on a schedule.

How many fortnights are between two dates?

Divide the calendar days by fourteen. A span of 358 days gives 25.57 fortnights, meaning 25 complete fourteen-day blocks with 8 days left over. Fortnightly payroll cycles, common in Australia, New Zealand, Ireland and the United Kingdom, count only the complete blocks, so a 358-day period contains 25 full pay fortnights and a part period.

How many weekends fall between two dates?

A weekend counts when both its Saturday and its Sunday fall inside the span. From 1 January 2026 to 25 December 2026 there are 51 complete weekends, alongside 102 individual weekend days. A lone Saturday at the end of a span adds a weekend day without adding a weekend, which is why the two figures are reported separately rather than derived from each other.

How many working weeks are between two dates?

Count the weekdays in the span and divide by five. A 358-day period contains 256 weekdays, giving 51.2 working weeks. That figure ignores public holidays, which vary by country and by state, so a working-week count taken from a calendar span is an upper bound — subtract the holidays that fall on weekdays to get billable or contractual working time.

Does the calculator count both the start and end dates?

The start date counts as day zero, so 1 January to 8 January is exactly one week rather than one week and a day. Counting both endpoints — an inclusive count, the convention for hire periods, hotel nights and some notice periods — adds one day to the total. Enter the day after the final day to get an inclusive result.

Why do weeks between dates never need a leap-year adjustment?

A week is a fixed seven-day unit, unlike a month or a year, so dividing calendar days by seven works across any leap year without correction. The leap day is simply one more day in the total. Calculations run in UTC to sidestep daylight-saving transitions, which make two days a year 23 or 25 hours long.

Sources

Last reviewed: · Formula and sources verified by Syed Aqeel Ahmad Gillani. See the methodology for how every calculation is derived.

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