Expand description
strftime
/strptime
-inspired date and time formatting syntax.
§Specifiers
The following specifiers are available both to formatting and parsing.
Spec. | Example | Description |
---|---|---|
DATE SPECIFIERS: | ||
%Y | 2001 | The full proleptic Gregorian year, zero-padded to 4 digits. chrono supports years from -262144 to 262143. Note: years before 1 BCE or after 9999 CE, require an initial sign (+/-). |
%C | 20 | The proleptic Gregorian year divided by 100, zero-padded to 2 digits. 1 |
%y | 01 | The proleptic Gregorian year modulo 100, zero-padded to 2 digits. 1 |
%m | 07 | Month number (01–12), zero-padded to 2 digits. |
%b | Jul | Abbreviated month name. Always 3 letters. |
%B | July | Full month name. Also accepts corresponding abbreviation in parsing. |
%h | Jul | Same as %b . |
%d | 08 | Day number (01–31), zero-padded to 2 digits. |
%e | 8 | Same as %d but space-padded. Same as %_d . |
%a | Sun | Abbreviated weekday name. Always 3 letters. |
%A | Sunday | Full weekday name. Also accepts corresponding abbreviation in parsing. |
%w | 0 | Sunday = 0, Monday = 1, …, Saturday = 6. |
%u | 7 | Monday = 1, Tuesday = 2, …, Sunday = 7. (ISO 8601) |
%U | 28 | Week number starting with Sunday (00–53), zero-padded to 2 digits. 2 |
%W | 27 | Same as %U , but week 1 starts with the first Monday in that year instead. |
%G | 2001 | Same as %Y but uses the year number in ISO 8601 week date. 3 |
%g | 01 | Same as %y but uses the year number in ISO 8601 week date. 3 |
%V | 27 | Same as %U but uses the week number in ISO 8601 week date (01–53). 3 |
%j | 189 | Day of the year (001–366), zero-padded to 3 digits. |
%D | 07/08/01 | Month-day-year format. Same as %m/%d/%y . |
%x | 07/08/01 | Locale’s date representation (e.g., 12/31/99). |
%F | 2001-07-08 | Year-month-day format (ISO 8601). Same as %Y-%m-%d . |
%v | 8-Jul-2001 | Day-month-year format. Same as %e-%b-%Y . |
TIME SPECIFIERS: | ||
%H | 00 | Hour number (00–23), zero-padded to 2 digits. |
%k | 0 | Same as %H but space-padded. Same as %_H . |
%I | 12 | Hour number in 12-hour clocks (01–12), zero-padded to 2 digits. |
%l | 12 | Same as %I but space-padded. Same as %_I . |
%P | am | am or pm in 12-hour clocks. |
%p | AM | AM or PM in 12-hour clocks. |
%M | 34 | Minute number (00–59), zero-padded to 2 digits. |
%S | 60 | Second number (00–60), zero-padded to 2 digits. 4 |
%f | 26490000 | Number of nanoseconds since last whole second. 5 |
%.f | .026490 | Decimal fraction of a second. Consumes the leading dot. 5 |
%.3f | .026 | Decimal fraction of a second with a fixed length of 3. |
%.6f | .026490 | Decimal fraction of a second with a fixed length of 6. |
%.9f | .026490000 | Decimal fraction of a second with a fixed length of 9. |
%3f | 026 | Decimal fraction of a second like %.3f but without the leading dot. |
%6f | 026490 | Decimal fraction of a second like %.6f but without the leading dot. |
%9f | 026490000 | Decimal fraction of a second like %.9f but without the leading dot. |
%R | 00:34 | Hour-minute format. Same as %H:%M . |
%T | 00:34:60 | Hour-minute-second format. Same as %H:%M:%S . |
%X | 00:34:60 | Locale’s time representation (e.g., 23:13:48). |
%r | 12:34:60 AM | Locale’s 12 hour clock time. (e.g., 11:11:04 PM). Falls back to %X if the locale does not have a 12 hour clock format. |
TIME ZONE SPECIFIERS: | ||
%Z | ACST | Local time zone name. Skips all non-whitespace characters during parsing. Identical to %:z when formatting. 6 |
%z | +0930 | Offset from the local time to UTC (with UTC being +0000 ). |
%:z | +09:30 | Same as %z but with a colon. |
%::z | +09:30:00 | Offset from the local time to UTC with seconds. |
%:::z | +09 | Offset from the local time to UTC without minutes. |
%#z | +09 | Parsing only: Same as %z but allows minutes to be missing or present. |
DATE & TIME SPECIFIERS: | ||
%c | Sun Jul 8 00:34:60 2001 | Locale’s date and time (e.g., Thu Mar 3 23:05:25 2005). |
%+ | 2001-07-08T00:34:60.026490+09:30 | ISO 8601 / RFC 3339 date & time format. 7 |
%s | 994518299 | UNIX timestamp, the number of seconds since 1970-01-01 00:00 UTC. 8 |
SPECIAL SPECIFIERS: | ||
%t | Literal tab (\t ). | |
%n | Literal newline (\n ). | |
%% | Literal percent sign. |
It is possible to override the default padding behavior of numeric specifiers %?
.
This is not allowed for other specifiers and will result in the BAD_FORMAT
error.
Modifier | Description |
---|---|
%-? | Suppresses any padding including spaces and zeroes. (e.g. %j = 012 , %-j = 12 ) |
%_? | Uses spaces as a padding. (e.g. %j = 012 , %_j = 12 ) |
%0? | Uses zeroes as a padding. (e.g. %e = 9 , %0e = 09 ) |
Notes:
%C
,%y
: This is floor division, so 100 BCE (year number -99) will print-1
and99
respectively. ↩%U
: Week 1 starts with the first Sunday in that year. It is possible to have week 0 for days before the first Sunday. ↩%G
,%g
,%V
: Week 1 is the first week with at least 4 days in that year. Week 0 does not exist, so this should be used with%G
or%g
. ↩%S
: It accounts for leap seconds, so60
is possible. ↩%f
,%.f
:
%f
and%.f
are notably different formatting specifiers.
%f
counts the number of nanoseconds since the last whole second, while%.f
is a fraction of a second.
Example: 7μs is formatted as7000
with%f
, and formatted as.000007
with%.f
. ↩%Z
: Sincechrono
is not aware of timezones beyond their offsets, this specifier only prints the offset when used for formatting. The timezone abbreviation will NOT be printed. See this issue for more information.
Offset will not be populated from the parsed data, nor will it be validated. Timezone is completely ignored. Similar to the glibcstrptime
treatment of this format code.
It is not possible to reliably convert from an abbreviation to an offset, for example CDT can mean either Central Daylight Time (North America) or China Daylight Time. ↩%+
: Same as%Y-%m-%dT%H:%M:%S%.f%:z
, i.e. 0, 3, 6 or 9 fractional digits for seconds and colons in the time zone offset.
This format also supports having aZ
orUTC
in place of%:z
. They are equivalent to+00:00
.
Note that allT
,Z
, andUTC
are parsed case-insensitively.
The typicalstrftime
implementations have different (and locale-dependent) formats for this specifier. While Chrono’s format for%+
is far more stable, it is best to avoid this specifier if you want to control the exact output. ↩%s
: This is not padded and can be negative. For the purpose of Chrono, it only accounts for non-leap seconds so it slightly differs from ISO Cstrftime
behavior. ↩
Structs§
- Parsing iterator for
strftime
-like format strings.