Weeks Between Two Dates
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About this calculator
Find out how many weeks are between two dates. Useful for project planning, sprint scheduling, and tracking durations in weekly increments.
How it works
The calculator computes the total difference in seconds between the two dates, then divides by 604,800 (the number of seconds in one week: 7 days × 24 hours × 60 minutes × 60 seconds). The result includes decimals for partial weeks — so 2.5 weeks means two weeks and 3.5 days.
When to use this calculator
Obstetricians track pregnancy in weeks for developmental milestone monitoring. Agile development teams plan sprints in weekly increments. Fitness coaches design training programs in weekly blocks. Academic institutions schedule term lengths in weeks. Real estate agents calculate weeks until closing. Landlords determine lease duration in weeks for short-term rental agreements.
Examples
A due date 40 weeks after the first day of the last period is exactly 280 days out — the standard way pregnancy is dated.
From January 1 to December 31 of a common year is about 52.1 weeks.
Common spans in weeks
How long familiar date ranges are when measured in weeks:
| Date range | Weeks |
|---|---|
| One week | 1 |
| One month (avg) | 4.34857 |
| One year | 52.1786 |
| One decade | 521.786 |
Frequently asked questions
How many weeks are between two dates one year apart?
About 52.18 weeks, since a year is 365.25 days ÷ 7.
Why is the result not a whole number?
Unless the two dates are an exact multiple of 7 days apart, the count includes a decimal for the leftover days.
Is this good for pregnancy tracking?
Yes — set the start date to the first day of the last period and the end date to today to see the current gestational week.