StraightToolsDate Calculator
Add or subtract calendar days from any date.
Calendar days
This calculator includes weekends and holidays. Use the business-days calculator when you want weekdays only.
When to use this tool
Use the date calculator to add or subtract calendar days from a chosen starting date. It is useful for deadlines, travel planning, warranties, schedules, and checking future or past dates.
How the result is calculated
Calendar-day arithmetic advances through every day of the week. Entering a positive number moves forward; entering a negative number moves backward.
Worked example
Starting on August 18 and adding 30 calendar days lands in mid-September. Weekends still count because this tool is based on calendar days rather than workdays.
What to keep in mind
If a deadline uses business days, banking days, court days, or excludes holidays, use the business-day tool and verify the applicable holiday rules.
About our calculations
StraightTools is designed to show the method behind the answer, not just the result. Inputs are handled in your browser for this tool. For important financial, legal, medical, tax, safety, or contractual decisions, verify the result with an appropriate authoritative source or qualified professional.