Date arithmetic
Add or subtract date calculator
Add positive days or subtract negative days from a calendar date.
How to use this calculator
Enter Starting date and Days to add or subtract. Add positive days or subtract negative days from a calendar date. The answer updates when you change an input.
Understanding the result
Using UTC calendar arithmetic prevents daylight-saving transitions from shifting date-only results.
Common questions
What assumptions does this result use?
A positive value adds days; a negative value subtracts days.
Are intermediate values rounded?
No. The calculation retains JavaScript number precision internally and formats only the displayed result unless the stated method requires a discrete whole value.