Timestamp 0: the Unix epoch
Answer
0 is the Unix epoch: 00:00:00 UTC on Thursday 1 January 1970. Every Unix timestamp counts seconds from that instant; negative numbers are times before it.
0 read as seconds since 1970-01-01 00:00 UTC is Thursday, 1970-01-01 00:00:00 UTC.
- ISO 8601 (UTC)
1970-01-01T00:00:00Z- Your time zone
shown when JavaScript runs- RFC 2822 / email
Thu, 01 Jan 1970 00:00:00 +0000- HTTP date
Thu, 01 Jan 1970 00:00:00 GMT- Seconds
0- Milliseconds
0- Day of week (UTC)
Thursday- ISO week
1970-W01- Day of year
1- Fits in 32-bit signed time_t
yes
What to know
Displayed in a time zone west of Greenwich, timestamp 0 shows as 31 December 1969 (19:00 in New York). A date of "December 31, 1969" on a website almost always means an empty or zero timestamp was formatted in local time.
Unix time ignores leap seconds: it pretends every day has 86,400 seconds, so a timestamp maps to a UTC calendar time with simple arithmetic, and the moment of a leap second repeats a timestamp.
Gotchas
- Some systems treat 0 as "no value". If 1970 dates appear in your data, check for nulls that were converted to 0.
- Other epochs exist: Windows FILETIME counts 100-nanosecond intervals from 1601, Apple's Core Data from 2001, GPS time from 6 January 1980.