Datetime Format Specifiers Cheatsheet

A comprehensive reference for date and time formatting across Python, JavaScript, Java, C#, Go, and the ISO 8601 standard.

Python (strftime / strptime)

Used with datetime.strftime(), datetime.strptime(), and the date shell command.

Specifier Example Description
%a Mon Abbreviated weekday name
%A Monday Full weekday name
%w 1 Weekday as number (0 = Sunday, 6 = Saturday)
%d 05 Day of month, zero-padded
%-d 5 Day of month, no padding (platform-dependent)
%b Jan Abbreviated month name
%B January Full month name
%m 01 Month as zero-padded number
%-m 1 Month, no padding (platform-dependent)
%y 21 Year without century, zero-padded
%Y 2021 Year with century
%H 13 Hour (24-hour), zero-padded
%I 01 Hour (12-hour), zero-padded
%p PM AM or PM
%M 30 Minute, zero-padded
%S 45 Second, zero-padded
%f 000123 Microsecond, zero-padded to 6 digits
%z +0530 UTC offset (+HHMM or -HHMM)
%Z EST Time zone name
%j 365 Day of year, zero-padded
%U 52 Week number (Sunday as first day)
%W 52 Week number (Monday as first day)
%G 2021 ISO 8601 year
%u 1 ISO 8601 weekday (1 = Monday, 7 = Sunday)
%V 52 ISO 8601 week number
%c Mon Sep 4 09:50:06 2017 Locale date and time
%x 09/04/17 Locale date
%X 09:50:06 Locale time
%% % Literal percent sign

These specifiers also work in C, C++ (strftime), Ruby (Time#strftime), PHP (date()), and shell commands (date +'%Y-%m-%d').

JavaScript

Intl.DateTimeFormat / toLocaleDateString Options

new Intl.DateTimeFormat('en-US', options).format(date)
// or
date.toLocaleDateString('en-US', options)
Option Values Example Output
year "numeric", "2-digit" 2024, 24
month "numeric", "2-digit", "long", "short", "narrow" 1, 01, January, Jan, J
day "numeric", "2-digit" 5, 05
weekday "long", "short", "narrow" Monday, Mon, M
hour "numeric", "2-digit" 3, 03
minute "numeric", "2-digit" 5, 05
second "numeric", "2-digit" 9, 09
hour12 true, false 3 PM vs 15
timeZone "UTC", "America/New_York", etc. –
timeZoneName "long", "short" Eastern Standard Time, EST
era "long", "short", "narrow" Anno Domini, AD, A
fractionalSecondDigits 1, 2, 3 1, 12, 123

Moment.js / Day.js Format Tokens

Token Example Description
YYYY 2024 4-digit year
YY 24 2-digit year
MMMM January Full month name
MMM Jan Abbreviated month name
MM 01 Month, zero-padded
M 1 Month, no padding
DD 05 Day of month, zero-padded
D 5 Day of month, no padding
dddd Monday Full weekday name
ddd Mon Abbreviated weekday name
dd Mo 2-letter weekday
d 1 Day of week (0 = Sunday)
HH 13 Hour (24-hour), zero-padded
H 13 Hour (24-hour), no padding
hh 01 Hour (12-hour), zero-padded
h 1 Hour (12-hour), no padding
mm 05 Minute, zero-padded
m 5 Minute, no padding
ss 09 Second, zero-padded
s 9 Second, no padding
SSS 123 Milliseconds
A PM Uppercase AM/PM
a pm Lowercase am/pm
Z +05:30 UTC offset
ZZ +0530 UTC offset (compact)
X 1700000000 Unix timestamp (seconds)
x 1700000000000 Unix timestamp (milliseconds)

Java (DateTimeFormatter)

Pattern Example Description
yyyy 2024 4-digit year
yy 24 2-digit year
MMMM January Full month name
MMM Jan Abbreviated month name
MM 01 Month, zero-padded
M 1 Month, no padding
dd 05 Day of month, zero-padded
d 5 Day of month, no padding
EEEE Monday Full weekday name
EEE Mon Abbreviated weekday name
HH 13 Hour (24-hour), zero-padded
H 13 Hour (24-hour), no padding
hh 01 Hour (12-hour), zero-padded
h 1 Hour (12-hour), no padding
mm 30 Minute, zero-padded
ss 45 Second, zero-padded
SSS 123 Milliseconds
a PM AM/PM marker
z EST Time zone abbreviation
Z +0530 RFC 822 time zone
XXX +05:30 ISO 8601 time zone
VV America/New_York Time zone ID
G AD Era designator
D 189 Day of year
u 1 Day of week (1 = Monday)

C# (.NET DateTime Format Strings)

Standard Format Strings

Specifier Name Example Output
d Short date 1/15/2024
D Long date Monday, January 15, 2024
t Short time 3:30 PM
T Long time 3:30:45 PM
f Full (short time) Monday, January 15, 2024 3:30 PM
F Full (long time) Monday, January 15, 2024 3:30:45 PM
g General (short time) 1/15/2024 3:30 PM
G General (long time) 1/15/2024 3:30:45 PM
o Round-trip (ISO 8601) 2024-01-15T15:30:45.0000000
r RFC 1123 Mon, 15 Jan 2024 15:30:45 GMT
s Sortable 2024-01-15T15:30:45
u Universal sortable 2024-01-15 15:30:45Z

Custom Format Specifiers

Specifier Example Description
yyyy 2024 4-digit year
yy 24 2-digit year
MMMM January Full month name
MMM Jan Abbreviated month name
MM 01 Month, zero-padded
M 1 Month, no padding
dddd Monday Full weekday name
ddd Mon Abbreviated weekday name
dd 05 Day, zero-padded
d 5 Day, no padding
HH 15 Hour (24-hour), zero-padded
H 15 Hour (24-hour), no padding
hh 03 Hour (12-hour), zero-padded
h 3 Hour (12-hour), no padding
mm 30 Minute, zero-padded
ss 45 Second, zero-padded
fff 123 Milliseconds
tt PM AM/PM designator
zzz +05:30 UTC offset with colon
zz +05 UTC offset (hours only)
K +05:30 Time zone info

Go (time.Format)

Go uses a reference layout based on the reference time Mon Jan 2 15:04:05 MST 2006 (01/02 03:04:05 PM ‘06 -0700).

Layout Value Description Example
2006 4-digit year 2024
06 2-digit year 24
January Full month name January
Jan Abbreviated month name Jan
01 Month, zero-padded 01
1 Month, no padding 1
Monday Full weekday name Monday
Mon Abbreviated weekday name Mon
02 Day, zero-padded 05
2 Day, no padding 5
_2 Day, space-padded  5
15 Hour (24-hour) 15
03 Hour (12-hour), zero-padded 03
3 Hour (12-hour), no padding 3
04 Minute, zero-padded 04
05 Second, zero-padded 05
.000 Milliseconds (trailing zeros) .123
.999 Milliseconds (no trailing zeros) .123
.000000 Microseconds .123456
.000000000 Nanoseconds .123456789
PM AM/PM (uppercase) PM
pm am/pm (lowercase) pm
MST Time zone abbreviation EST
-0700 UTC offset (numeric) -0500
-07:00 UTC offset with colon -05:00
Z0700 UTC offset (Z for UTC) Z or -0500
Z07:00 UTC offset with colon (Z for UTC) Z or -05:00

Go Predefined Layouts

Constant Layout String
time.RFC3339 2006-01-02T15:04:05Z07:00
time.RFC3339Nano 2006-01-02T15:04:05.999999999Z07:00
time.RFC1123 Mon, 02 Jan 2006 15:04:05 MST
time.RFC822 02 Jan 06 15:04 MST
time.Kitchen 3:04PM
time.DateTime 2006-01-02 15:04:05
time.DateOnly 2006-01-02
time.TimeOnly 15:04:05

ISO 8601 Reference

Format Example Description
YYYY-MM-DD 2024-01-15 Date
YYYY-MM-DDThh:mm:ss 2024-01-15T15:30:45 Date and time (local)
YYYY-MM-DDThh:mm:ssZ 2024-01-15T15:30:45Z Date and time (UTC)
YYYY-MM-DDThh:mm:ss+hh:mm 2024-01-15T15:30:45+05:30 Date and time with offset
YYYY-Www 2024-W03 Week date (week 3 of 2024)
YYYY-Www-D 2024-W03-1 Week date with day (Monday)
YYYY-DDD 2024-015 Ordinal date (day 15 of 2024)
hh:mm:ss 15:30:45 Time only
PnYnMnDTnHnMnS P1Y2M3DT4H5M6S Duration (1y 2m 3d 4h 5m 6s)
start/end 2024-01-01/2024-12-31 Time interval
start/duration 2024-01-01/P30D Time interval with duration
Rn/start/duration R5/2024-01-01/P1M Repeating interval (5 times)

Common Formats Across Languages

How to produce common date/time formats in each language.

“2024-01-15” (ISO Date)

Language Code
Python dt.strftime('%Y-%m-%d')
JavaScript dt.toISOString().slice(0, 10)
Java dt.format(DateTimeFormatter.ISO_LOCAL_DATE)
C# dt.ToString("yyyy-MM-dd")
Go t.Format("2006-01-02")

“Jan 15, 2024” (Readable Date)

Language Code
Python dt.strftime('%b %d, %Y')
JavaScript (Intl) new Intl.DateTimeFormat('en-US', {month:'short', day:'numeric', year:'numeric'}).format(dt)
JavaScript (dayjs) dayjs(dt).format('MMM DD, YYYY')
Java dt.format(DateTimeFormatter.ofPattern("MMM dd, yyyy"))
C# dt.ToString("MMM dd, yyyy")
Go t.Format("Jan 02, 2006")

“3:30 PM” (12-Hour Time)

Language Code
Python dt.strftime('%-I:%M %p')
JavaScript (Intl) new Intl.DateTimeFormat('en-US', {hour:'numeric', minute:'2-digit', hour12:true}).format(dt)
JavaScript (dayjs) dayjs(dt).format('h:mm A')
Java dt.format(DateTimeFormatter.ofPattern("h:mm a"))
C# dt.ToString("h:mm tt")
Go t.Format("3:04 PM")

“Monday, January 15” (Full Weekday + Date)

Language Code
Python dt.strftime('%A, %B %d')
JavaScript (Intl) new Intl.DateTimeFormat('en-US', {weekday:'long', month:'long', day:'numeric'}).format(dt)
JavaScript (dayjs) dayjs(dt).format('dddd, MMMM D')
Java dt.format(DateTimeFormatter.ofPattern("EEEE, MMMM d"))
C# dt.ToString("dddd, MMMM d")
Go t.Format("Monday, January 2")

“2024-01-15T15:30:45Z” (ISO 8601 Full)

Language Code
Python dt.strftime('%Y-%m-%dT%H:%M:%SZ')
JavaScript dt.toISOString()
Java dt.format(DateTimeFormatter.ISO_INSTANT)
C# dt.ToUniversalTime().ToString("o")
Go t.UTC().Format(time.RFC3339)