=begin
Full Ruby strftime Cheatsheet:
Date (Year, Month, Day)
%Y — Year with century (e.g., 2026)
%y — Year without century (00–99)
%C — Century (year / 100)
%m — Month (01–12), zero‑padded
%_m — Month, space‑padded
%-m — Month, no padding
%B — Full month name (January)
%b / %h — Abbreviated month name (Jan)
%d — Day of month (01–31), zero‑padded
%-d — Day, no padding
%e — Day, space‑padded
%j — Day of year (001–366)
Time (Hour, Minute, Second, Subsecond)
%H — Hour (00–23), zero‑padded
%k — Hour (0–23), space‑padded
%I — Hour (01–12), zero‑padded
%l — Hour (1–12), space‑padded
%M — Minute (00–59)
%S — Second (00–60, leap second)
%L — Milliseconds (000–999)
%N — Nanoseconds (9 digits)
%3N → milliseconds
%6N → microseconds
%9N → nanoseconds
%p — AM/PM (uppercase)
%P — am/pm (lowercase)
Time Zone
%z — Offset (+0900)
%:z — Offset with colon (+09:00)
%::z — Offset with seconds (+09:00:00)
%Z — Time zone abbreviation (OS‑dependent)
Weekday
%A — Full weekday name (Sunday)
%a — Abbreviated weekday (Sun)
%u — Weekday (1=Mon … 7=Sun)
%w — Weekday (0=Sun … 6=Sat)
ISO Week‑Based Year
%G — ISO week‑based year
%g — Last 2 digits of ISO year
%V — ISO week number (01–53)
Seconds Since Epoch
%s — Unix timestamp (seconds)
%Q — Unix timestamp (milliseconds)
Literal Characters
%n — Newline
%t — Tab
%% — Literal %
Composite / Convenience Formats
%c — Preferred date+time (%a %b %e %T %Y)
%D — %m/%d/%y
%F — ISO 8601 date (%Y-%m-%d)
%v — VMS date (%e-%b-%Y)
%x — Locale date
%X — Locale time
%r — 12‑hour time (%I:%M:%S %p)
%R — 24‑hour time (%H:%M)
%T — 24‑hour time (%H:%M:%S)
%+ — Date with time zone (%a %b %e %H:%M:%S %Z %Y)
Padding & Case Flags
- — No padding
_ — Space padding
0 — Zero padding
^ — Uppercase result
# — Change case
: — Use colons for %z
=end
require "time"
now = Time.now
def show(label, pattern, now)
puts "#{label.ljust(30)} #{pattern.ljust(12)} → #{now.strftime(pattern)}"
end
puts "=== Ruby strftime Full Cheatsheet Demo ==="
puts "Current time: #{now}"
puts "-" * 60
# --- YEAR ---
show("Year (4 digits)", "%Y", now)
show("Year (2 digits)", "%y", now)
show("Century", "%C", now)
# --- MONTH ---
show("Month (01-12)", "%m", now)
show("Month (1-12, space)", "%_m", now)
show("Month (1-12, no pad)", "%-m", now)
show("Month name (short)", "%b", now)
show("Month name (full)", "%B", now)
# --- DAY ---
show("Day (01-31)", "%d", now)
show("Day (1-31, space)", "%e", now)
show("Day of year (001-366)", "%j", now)
# --- WEEKDAY ---
show("Weekday (0=Sun)", "%w", now)
show("Weekday (1=Mon)", "%u", now)
show("Weekday name (short)", "%a", now)
show("Weekday name (full)", "%A", now)
# --- TIME ---
show("Hour (00-23)", "%H", now)
show("Hour (0-23, space)", "%k", now)
show("Hour (01-12)", "%I", now)
show("Hour (1-12, space)", "%l", now)
show("Minute (00-59)", "%M", now)
show("Second (00-60)", "%S", now)
show("Millisecond", "%L", now)
show("Nanoseconds", "%N", now)
show("AM/PM", "%p", now)
show("am/pm", "%P", now)
# --- TIME ZONE ---
show("Timezone abbrev", "%Z", now)
show("Offset (+0900)", "%z", now)
show("Offset (+09:00)", "%:z", now)
show("Offset (+09:00:00)", "%::z", now)
# --- ISO WEEK YEAR ---
show("ISO week year", "%G", now)
show("ISO week year (2-digit)", "%g", now)
show("ISO week number", "%V", now)
# --- UNIX TIME ---
show("Unix timestamp (sec)", "%s", now)
show("Unix timestamp (ms)", "%Q", now)
# --- COMPOSITE ---
show("Preferred date+time", "%c", now)
show("mm/dd/yy", "%D", now)
show("ISO date", "%F", now)
show("VMS date", "%v", now)
show("Locale date", "%x", now)
show("Locale time", "%X", now)
show("12-hour time", "%r", now)
show("24-hour time (HH:MM)", "%R", now)
show("24-hour time (HH:MM:SS)", "%T", now)
show("Full date with TZ", "%+", now)
# --- LITERALS ---
show("Literal %", "%%", now)
show("Newline", "%n", now)
show("Tab", "%t", now)
=begin
run:
=== Ruby strftime Full Cheatsheet Demo ===
Current time: 2026-05-21 05:23:28 +0000
------------------------------------------------------------
Year (4 digits) %Y → 2026
Year (2 digits) %y → 26
Century %C → 20
Month (01-12) %m → 05
Month (1-12, space) %_m → 5
Month (1-12, no pad) %-m → 5
Month name (short) %b → May
Month name (full) %B → May
Day (01-31) %d → 21
Day (1-31, space) %e → 21
Day of year (001-366) %j → 141
Weekday (0=Sun) %w → 4
Weekday (1=Mon) %u → 4
Weekday name (short) %a → Thu
Weekday name (full) %A → Thursday
Hour (00-23) %H → 05
Hour (0-23, space) %k → 5
Hour (01-12) %I → 05
Hour (1-12, space) %l → 5
Minute (00-59) %M → 23
Second (00-60) %S → 28
Millisecond %L → 171
Nanoseconds %N → 171670708
AM/PM %p → AM
am/pm %P → am
Timezone abbrev %Z → UTC
Offset (+0900) %z → +0000
Offset (+09:00) %:z → +00:00
Offset (+09:00:00) %::z → +00:00:00
ISO week year %G → 2026
ISO week year (2-digit) %g → 26
ISO week number %V → 21
Unix timestamp (sec) %s → 1779341008
Unix timestamp (ms) %Q → %Q
Preferred date+time %c → Thu May 21 05:23:28 2026
mm/dd/yy %D → 05/21/26
ISO date %F → 2026-05-21
VMS date %v → 21-MAY-2026
Locale date %x → 05/21/26
Locale time %X → 05:23:28
12-hour time %r → 05:23:28 AM
24-hour time (HH:MM) %R → 05:23
24-hour time (HH:MM:SS) %T → 05:23:28
Full date with TZ %+ → %+
Literal % %% → %
Newline %n →
Tab %t →
=end
