A quick reference guide comparing format specifiers across standard C / UNIX strftime and modern JavaScript libraries (Moment.js, date-fns, dayjs).
UNIX strftime Format Specifiers
Standard formatting used by C, POSIX, Python (datetime.strftime), Ruby (Time#strftime), and shell utilities.
Date Tokens
| Specifier | Description | Example |
|---|---|---|
%Y |
4-digit Year | 2026 |
%y |
2-digit Year (00–99) | 26 |
%m |
Month number (01–12) | 10 |
%B |
Full month name | October |
%b / %h |
Abbreviated month name | Oct |
%d |
Day of the month, zero-padded (01–31) | 05 |
%e |
Day of the month, space-padded ( 1–31) | 5 |
%A |
Full weekday name | Sunday |
%a |
Abbreviated weekday name | Sun |
%w |
Day of the week (0 = Sunday .. 6 = Saturday) | 0 |
%j |
Day of the year (001–366) | 278 |
Time Tokens
| Specifier | Description | Example |
|---|---|---|
%H |
Hour in 24-hour format (00–23) | 14 |
%I |
Hour in 12-hour format (01–12) | 02 |
%M |
Minute (00–59) | 30 |
%S |
Second (00–59) | 45 |
%p |
AM or PM designation | PM |
%z |
UTC offset (+HHMM or -HHMM) | +0000 |
%Z |
Time zone abbreviation | UTC |
%s |
Unix epoch timestamp (seconds since Jan 1 1970) | 1792944000 |
Moment.js / date-fns Format Tokens
Formatting tokens used by Moment.js, Day.js, date-fns, and Java SimpleDateFormat.
Date & Time Tokens
| Token | Description | Example |
|---|---|---|
YYYY |
4-digit Year | 2026 |
YY |
2-digit Year | 26 |
M / MM |
Month number (1–12 / 01–12) | 5 / 05 |
MMM / MMMM |
Short / Full month name | May / May |
D / DD |
Day of month (1–31 / 01–31) | 7 / 07 |
Do |
Day of month with ordinal | 7th |
d / dddd |
Day of week index / Full name | 0 / Sunday |
H / HH |
24-hour format (0–23 / 00–23) | 9 / 09 |
h / hh |
12-hour format (1–12 / 01–12) | 9 / 09 |
m / mm |
Minute (0–59 / 00–59) | 5 / 05 |
s / ss |
Second (0–59 / 00–59) | 2 / 02 |
a / A |
am/pm or AM/PM | pm / PM |
Z / ZZ |
Timezone offset | +08:00 / +0800 |
X |
Unix timestamp (seconds) | 1410715640 |
x |
Unix timestamp (milliseconds) | 1410715640579 |
Common Presets Comparison
| Representation | strftime |
Moment / date-fns | Example Output |
|---|---|---|---|
| ISO 8601 Date | %Y-%m-%d |
YYYY-MM-DD |
2026-10-25 |
| 12-Hour Time | %I:%M %p |
hh:mm A |
02:30 PM |
| 24-Hour Time with Sec | %H:%M:%S |
HH:mm:ss |
14:30:45 |
| Readable Date | %B %e, %Y |
MMMM D, YYYY |
October 25, 2026 |