Ruby strftime Format Directives Reference

Ruby strftime Directives

Ruby's Time#strftime and Date#strftime methods use percent-prefixed directives inherited from the C standard library, very similar to Python. However, Ruby includes several extra directives and modifier flags.

Core Directives

Directive	Meaning	Example
%Y	Year (4-digit)	2026
%y	Year (2-digit)	26
%m	Month (zero-padded)	02
%-m	Month (no padding)	2
%B	Full month name	February
%b / %h	Abbreviated month	Feb
%d	Day (zero-padded)	28
%e	Day (space-padded)	28
%-d	Day (no padding)	28
%A	Full weekday	Saturday
%a	Abbreviated weekday	Sat
%u	Weekday (1=Monday)	6
%w	Weekday (0=Sunday)	6
%H	Hour 24h (zero-padded)	14
%k	Hour 24h (space-padded)	14
%I	Hour 12h (zero-padded)	02
%l	Hour 12h (space-padded)	2
%M	Minute	30
%S	Second	00
%L	Millisecond	123
%N	Nanosecond	123456789
%p	AM/PM (uppercase)	PM
%P	am/pm (lowercase)	pm
%j	Day of year	059
%z	Timezone offset	+0900
%:z	Offset with colon	+09:00
%Z	Timezone name	JST
%s	Unix timestamp	1772236800

Ruby-Specific Extras

Ruby includes directives not found in Python:

• %e — Space-padded day ( 3 instead of 03)
• %k — Space-padded 24h hour
• %l — Space-padded 12h hour
• %P — Lowercase am/pm (Python's %p is uppercase)
• %L — Milliseconds (3 digits)
• %N — Fractional seconds (up to 9 digits for nanoseconds)
• %:z — Colon-separated offset (+09:00 vs +0900)
• %s — Unix timestamp as string

Modifier Flags

Ruby supports modifier flags between % and the directive:

Flag	Effect	Example
-	No padding	%-d → 3
_	Space padding	%_m → 2
0	Zero padding (default)	%0d → 03
^	Uppercase	%^b → FEB
#	Case swap	%#B → FEBRUARY

Common Patterns

Time.now.strftime("%Y-%m-%d %H:%M:%S")        # "2026-02-28 14:30:00"
Time.now.strftime("%B %-d, %Y")                # "February 28, 2026"
Time.now.strftime("%a, %d %b %Y %H:%M:%S %z") # RFC 2822
Time.now.strftime("%Y-%m-%dT%H:%M:%S%:z")     # ISO 8601 with offset
Time.now.strftime("%I:%M %p")                  # "02:30 PM"
Time.now.strftime("%s")                        # Unix timestamp

Parsing with strptime

Time.strptime("2026-02-28 14:30", "%Y-%m-%d %H:%M")
Date.strptime("28/02/2026", "%d/%m/%Y")