Days between December 31, 1999 and January 1, 2000
There are 1 days between these two dates — y2k — one day.
Time Until
1 days
Days
1
Weeks
0
+1 days
Months
0
December 31, 1999 to January 1, 2000, broken down
- Days1
- Weeks0 + 1d
- Months0
- Years0y 0m
The count is exclusive of the start date and inclusive of the end date: day one is December 31, 1999 plus 24 hours. Weekends and public holidays are included — for working days only, use the business days calculator.
The turn from 31 December 1999 to 1 January 2000 is a single day, but it is one of the most-searched date gaps because of the Y2K computer bug. The concern was that two-digit year fields would read "00" as 1900.
Method & sources
Day counts use the Gregorian calendar and are computed on calendar dates in UTC, so daylight-saving changes never add or remove a day. The count excludes the start date and includes the end date — the same convention as subtracting one date from another.
Page last updated: October 1, 2026
Frequently asked questions
How many days are between December 31, 1999 and January 1, 2000?
There are exactly 1 days between the two dates, counting the end date and not the start date.
How many weeks is that?
1 days is 0 weeks and 1 day.
How many months and years is that?
About 0 months and 1 day (0 months in total).
Other date spans
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