A Timestamp represents a point in time independent of any time zone or local
calendar, encoded as a count of seconds and fractions of seconds at
nanosecond resolution. The count is relative to an epoch at UTC midnight on
January 1, 1970, in the proleptic Gregorian calendar which extends the
Gregorian calendar backwards to year one.
All minutes are 60 seconds long. Leap seconds are “smeared” so that no leap
second table is needed for interpretation, using a 24-hour linear
smear.
The range is from 0001-01-01T00:00:00Z to 9999-12-31T23:59:59.999999999Z. By
restricting to that range, we ensure that we can convert to and from RFC
3339 date strings.
Examples
Example 1: Compute Timestamp from POSIX time().
Timestamp timestamp;
timestamp.set_seconds(time(NULL));
timestamp.set_nanos(0);
Example 2: Compute Timestamp from POSIX gettimeofday().
struct timeval tv;
gettimeofday(&tv, NULL);
Timestamp timestamp;
timestamp.set_seconds(tv.tv_sec);
timestamp.set_nanos(tv.tv_usec * 1000);
Example 3: Compute Timestamp from Win32 GetSystemTimeAsFileTime().
FILETIME ft;
GetSystemTimeAsFileTime(&ft);
UINT64 ticks = (((UINT64)ft.dwHighDateTime) << 32) | ft.dwLowDateTime;
// A Windows tick is 100 nanoseconds. Windows epoch 1601-01-01T00:00:00Z
// is 11644473600 seconds before Unix epoch 1970-01-01T00:00:00Z.
Timestamp timestamp;
timestamp.set_seconds((INT64) ((ticks / 10000000) - 11644473600LL));
timestamp.set_nanos((INT32) ((ticks % 10000000) * 100));
Example 4: Compute Timestamp from Java System.currentTimeMillis().
long millis = System.currentTimeMillis();
Timestamp timestamp = Timestamp.newBuilder().setSeconds(millis / 1000)
.setNanos((int) ((millis % 1000) * 1000000)).build();
Example 5: Compute Timestamp from Java Instant.now().
Instant now = Instant.now();
Timestamp timestamp =
Timestamp.newBuilder().setSeconds(now.getEpochSecond())
.setNanos(now.getNano()).build();
Example 6: Compute Timestamp from current time in Python.
timestamp = Timestamp()
timestamp.GetCurrentTime()
JSON Mapping
In JSON format, the Timestamp type is encoded as a string in the
RFC 3339 format. That is, the
format is “{year}-{month}-{day}T{hour}:{min}:{sec}[.{frac_sec}]Z”
where {year} is always expressed using four digits while {month}, {day},
{hour}, {min}, and {sec} are zero-padded to two digits each. The fractional
seconds, which can go up to 9 digits (i.e. up to 1 nanosecond resolution),
are optional. The “Z” suffix indicates the timezone (“UTC”); the timezone
is required. A proto3 JSON serializer should always use UTC (as indicated by
“Z”) when printing the Timestamp type and a proto3 JSON parser should be
able to accept both UTC and other timezones (as indicated by an offset).
For example, “2017-01-15T01:30:15.01Z” encodes 15.01 seconds past
01:30 UTC on January 15, 2017.
In JavaScript, one can convert a Date object to this format using the
standard
toISOString()
method. In Python, a standard datetime.datetime object can be converted
to this format using
strftime with
the time format spec ‘%Y-%m-%dT%H:%M:%S.%fZ’. Likewise, in Java, one can use
the Joda Time’s ISODateTimeFormat.dateTime() to obtain a formatter capable of generating timestamps in this format.
