D+ day calculator
Show how many days have passed since a start date as D+n. Day one is D+0, so a start on 2025-01-01 reads D+100 on 2025-04-11.
Uses the device date shown in this browser.
What to know
The D+ page measures elapsed time from a Start date up to today on your device. The result is printed as D+ followed by the whole days that have passed, and the label under it reads Days since start.
The start date itself is D+0, not D+1. A start of 2025-01-01 reads D+100 on 2025-04-11, because January contributes 31 days, February 28, March 31 and April 10 more. Anniversaries counted as day 1 on the start day, such as a 100-day milestone, therefore arrive at D+99.
Only past or present starts are accepted. If you pick a start date after today, the field is flagged with the message that the start date cannot be after today, and the result stays blank. Use the D-day page for events that have not happened yet.
The same count can be rebuilt with the date-difference page by setting the End date to today, but that page prints a plain number of days instead of the D+ notation and accepts future dates as well.
It suits streaks, relationship milestones, time since a launch, days without an incident and elapsed days on a project. Because the start day is D+0, comparing two events is easy: the one with the larger D+ number started earlier.
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How to use D+ day calculator
- Enter Start date 2025-01-01.
- Let your device supply today, for example 2025-04-11.
- Read Days since start, which shows D+100.
- To find the 100th-day date counted from day one, add 99 on the add-days page instead.
Quick answers
Why does the first day read D+0 and not D+1?
Elapsed time starts at zero on the start date. If you want day 1 on the start date, add 1 to the number shown.
Can I use a start date in the future?
No. The page shows an error when the start is after today, since D+ only describes time that has already passed.
How do I find the date of the 100th day of a relationship?
Counting the first day as day 1, add 99 days to the start date on the add-days page. From 2025-01-01 that lands on 2025-04-10.