Time & Date / calculator
Date calculator
Calculate the difference between two dates or move a date forward or backward using deterministic calendar arithmetic.
What this tool does
Choose a date operation, enter dates as YYYY-MM-DD, and see exactly how the calendar calculation is counted.
Calculator
Choose an operation and enter your dates.
Use calendar dates in YYYY-MM-DD format. Differences are explicitly exclusive or inclusive; date arithmetic is time-zone independent.
Calculation result
Your result
Enter details to see the estimate.
The result separates wall area, coverage, waste allowance, and the rounded quantity to consider buying.
How it works
Date differences count whole calendar days. Exclusive mode counts the gap between dates; inclusive mode counts both the start and end dates. Add and subtract operations move by calendar days or seven-day weeks.
Assumptions
- Dates are date-only values in YYYY-MM-DD format, not timestamps.
- Date arithmetic does not depend on a browser time zone or daylight-saving transition.
- Exclusive difference does not count the start date; inclusive difference counts both endpoints.
Limitations
- This tool does not calculate elapsed hours or time-zone-aware durations.
- It does not account for business days, holidays, or locale-specific calendars.
- Dates outside the supported year range are rejected.
Good to know
Frequently asked questions
What is exclusive date difference?
Exclusive difference counts the days after the start date up to the end date. January 1 to January 2 is 1 day.
What is inclusive date difference?
Inclusive difference counts both the start and end dates. January 1 to January 2 is 2 calendar days inclusive.
Does daylight saving time change the result?
No. This calculator works with calendar dates only, so daylight-saving and local-time transitions do not change the day result.
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