Python Datetime Format Cheat Sheet

Quick reference for datetime, format directives, parsing, formatting, and timezones. For the full tutorial see Datetime.

1. Format Directives

Code	Meaning	Example
`%Y`	Year, 4-digit	`2026`
`%y`	Year, 2-digit	`26`
`%m`	Month, zero-padded	`05`
`%B`	Month, full name	`May`
`%b`	Month, short name	`May`
`%d`	Day of month, zero-padded	`14`
`%j`	Day of year (001..366)	`134`
`%a`	Weekday, short	`Thu`
`%A`	Weekday, full	`Thursday`
`%w`	Weekday number (Sun=0)	`4`
`%U`	Week number (Sunday-start)	`19`
`%W`	Week number (Monday-start)	`19`
`%H`	Hour 24h, zero-padded	`09`
`%I`	Hour 12h, zero-padded	`09`
`%p`	AM / PM	`AM`
`%M`	Minute, zero-padded	`30`
`%S`	Second, zero-padded	`45`
`%f`	Microsecond	`000123`
`%z`	UTC offset	`+0530`
`%Z`	Timezone name	`IST`
`%c`	Locale date+time	`Thu May 14 09:30:45 2026`
`%x`	Locale date	`05/14/26`
`%X`	Locale time	`09:30:45`
`%%`	Literal `%`	`%`

2. Creating Datetimes

python

from datetime import date, time, datetime, timedelta, timezone
from zoneinfo import ZoneInfo

date(2026, 5, 14)                                # 2026-05-14
time(9, 30, 0)                                   # 09:30:00
datetime(2026, 5, 14, 9, 30)                     # naive

datetime.now()                                   # naive local
datetime.now(tz=ZoneInfo("Asia/Kolkata"))        # aware
datetime.now(tz=timezone.utc)                    # aware UTC
date.today()                                     # date only

3. Parsing Strings

python

datetime.strptime("2026-05-14", "%Y-%m-%d")
datetime.strptime("14 May 2026 09:30", "%d %b %Y %H:%M")

date.fromisoformat("2026-05-14")
time.fromisoformat("09:30:00")

# 3.11+ — very forgiving, accepts most ISO 8601 forms
datetime.fromisoformat("2026-05-14T09:30:45+05:30")
datetime.fromisoformat("2026-05-14 09:30:45Z")

+ setup added so this can run · defines datetime, date, time

# Lightweight mock for objects whose attributes/methods aren't critical
class _AutoMock:
    def __init__(self, name='mock'): self._name = name
    def __getattr__(self, k): return _AutoMock(self._name + '.' + k)
    def __call__(self, *a, **kw):
        print('-> ' + self._name + '() called')
        return _AutoMock(self._name + '()')
    def __repr__(self): return '<mock ' + self._name + '>'
    def __str__(self): return '<mock ' + self._name + '>'
    def __bool__(self): return True
    def __iter__(self): return iter([])
    def __len__(self): return 0
    def __getitem__(self, k): return _AutoMock(self._name + '[...]')
    def __setitem__(self, k, v): pass
    def __enter__(self): return self
    def __exit__(self, *a): return False
    async def __aenter__(self): return self
    async def __aexit__(self, *a): return False
    def __add__(self, o): return self
    def __radd__(self, o): return self
    def __sub__(self, o): return self
    def __mul__(self, o): return self
    def __rmul__(self, o): return self
    def __truediv__(self, o): return self
    def __eq__(self, o): return isinstance(o, _AutoMock)
    def __hash__(self): return hash(self._name)
    def __lt__(self, o): return True
    def __le__(self, o): return True
    def __gt__(self, o): return False
    def __ge__(self, o): return False
    def __mro_entries__(self, bases): return (object,)

datetime = _AutoMock('datetime')
date = _AutoMock('date')
time = _AutoMock('time')

4. Formatting

python

dt = datetime(2026, 5, 14, 9, 30, 45)

dt.strftime("%Y-%m-%d %H:%M")        # '2026-05-14 09:30'
dt.isoformat()                        # '2026-05-14T09:30:45'
dt.isoformat(sep=" ", timespec="minutes")   # '2026-05-14 09:30'

# f-string format spec passes through to strftime
f"{dt:%d %b %Y, %I:%M %p}"            # '14 May 2026, 09:30 AM'

+ setup added so this can run · defines datetime

# Lightweight mock for objects whose attributes/methods aren't critical
class _AutoMock:
    def __init__(self, name='mock'): self._name = name
    def __getattr__(self, k): return _AutoMock(self._name + '.' + k)
    def __call__(self, *a, **kw):
        print('-> ' + self._name + '() called')
        return _AutoMock(self._name + '()')
    def __repr__(self): return '<mock ' + self._name + '>'
    def __str__(self): return '<mock ' + self._name + '>'
    def __bool__(self): return True
    def __iter__(self): return iter([])
    def __len__(self): return 0
    def __getitem__(self, k): return _AutoMock(self._name + '[...]')
    def __setitem__(self, k, v): pass
    def __enter__(self): return self
    def __exit__(self, *a): return False
    async def __aenter__(self): return self
    async def __aexit__(self, *a): return False
    def __add__(self, o): return self
    def __radd__(self, o): return self
    def __sub__(self, o): return self
    def __mul__(self, o): return self
    def __rmul__(self, o): return self
    def __truediv__(self, o): return self
    def __eq__(self, o): return isinstance(o, _AutoMock)
    def __hash__(self): return hash(self._name)
    def __lt__(self, o): return True
    def __le__(self, o): return True
    def __gt__(self, o): return False
    def __ge__(self, o): return False
    def __mro_entries__(self, bases): return (object,)

def datetime(*_a, **_kw):
    print('-> datetime() called')
    return _AutoMock('datetime()')

5. timedelta

python

from datetime import timedelta

td = timedelta(days=7, hours=3, minutes=15)
td.total_seconds()                    # 616500.0
td.days, td.seconds                   # (7, 11700)

# Arithmetic
later = dt + timedelta(days=30)
delta = later - dt                    # timedelta(days=30)

# Multiplication / division
fortnight = 2 * timedelta(weeks=1)
half = timedelta(hours=1) / 2         # timedelta(minutes=30)

+ setup added so this can run · defines dt

# Lightweight mock for objects whose attributes/methods aren't critical
class _AutoMock:
    def __init__(self, name='mock'): self._name = name
    def __getattr__(self, k): return _AutoMock(self._name + '.' + k)
    def __call__(self, *a, **kw):
        print('-> ' + self._name + '() called')
        return _AutoMock(self._name + '()')
    def __repr__(self): return '<mock ' + self._name + '>'
    def __str__(self): return '<mock ' + self._name + '>'
    def __bool__(self): return True
    def __iter__(self): return iter([])
    def __len__(self): return 0
    def __getitem__(self, k): return _AutoMock(self._name + '[...]')
    def __setitem__(self, k, v): pass
    def __enter__(self): return self
    def __exit__(self, *a): return False
    async def __aenter__(self): return self
    async def __aexit__(self, *a): return False
    def __add__(self, o): return self
    def __radd__(self, o): return self
    def __sub__(self, o): return self
    def __mul__(self, o): return self
    def __rmul__(self, o): return self
    def __truediv__(self, o): return self
    def __eq__(self, o): return isinstance(o, _AutoMock)
    def __hash__(self): return hash(self._name)
    def __lt__(self, o): return True
    def __le__(self, o): return True
    def __gt__(self, o): return False
    def __ge__(self, o): return False
    def __mro_entries__(self, bases): return (object,)

dt = _AutoMock('dt')

6. Timezones (zoneinfo, 3.9+)

python

from datetime import datetime, timezone
from zoneinfo import ZoneInfo

ist = ZoneInfo("Asia/Kolkata")
ny  = ZoneInfo("America/New_York")

now_utc = datetime.now(timezone.utc)
now_utc.astimezone(ist)                # convert
naive = datetime(2026, 5, 14, 9, 30)
aware = naive.replace(tzinfo=ist)      # attach without conversion

On Windows install tzdata first: pip install tzdata.

Common Patterns

python

# Start of today
from datetime import datetime, time, timedelta, date
start = datetime.combine(date.today(), time.min)

# End of today
end = datetime.combine(date.today(), time.max)

# Yesterday
yesterday = date.today() - timedelta(days=1)

# First day of current month
first = date.today().replace(day=1)

# Last day of current month
import calendar
today = date.today()
last_day = today.replace(day=calendar.monthrange(today.year, today.month)[1])

# Next Monday
def next_weekday(d, weekday):
    days = (weekday - d.weekday()) % 7 or 7
    return d + timedelta(days=days)

# ISO week number
year, week, dow = date.today().isocalendar()

# Age in whole years
from datetime import date
def age(dob):
    t = date.today()
    return t.year - dob.year - ((t.month, t.day) < (dob.month, dob.day))

# Unix timestamp <-> datetime
ts = datetime.now(timezone.utc).timestamp()
back = datetime.fromtimestamp(ts, tz=timezone.utc)

# Format duration human-friendly (rough)
def hms(td):
    s = int(td.total_seconds())
    return f"{s // 3600:02d}:{s % 3600 // 60:02d}:{s % 60:02d}"

+ setup added so this can run · defines timezone

# Lightweight mock for objects whose attributes/methods aren't critical
class _AutoMock:
    def __init__(self, name='mock'): self._name = name
    def __getattr__(self, k): return _AutoMock(self._name + '.' + k)
    def __call__(self, *a, **kw):
        print('-> ' + self._name + '() called')
        return _AutoMock(self._name + '()')
    def __repr__(self): return '<mock ' + self._name + '>'
    def __str__(self): return '<mock ' + self._name + '>'
    def __bool__(self): return True
    def __iter__(self): return iter([])
    def __len__(self): return 0
    def __getitem__(self, k): return _AutoMock(self._name + '[...]')
    def __setitem__(self, k, v): pass
    def __enter__(self): return self
    def __exit__(self, *a): return False
    async def __aenter__(self): return self
    async def __aexit__(self, *a): return False
    def __add__(self, o): return self
    def __radd__(self, o): return self
    def __sub__(self, o): return self
    def __mul__(self, o): return self
    def __rmul__(self, o): return self
    def __truediv__(self, o): return self
    def __eq__(self, o): return isinstance(o, _AutoMock)
    def __hash__(self): return hash(self._name)
    def __lt__(self, o): return True
    def __le__(self, o): return True
    def __gt__(self, o): return False
    def __ge__(self, o): return False
    def __mro_entries__(self, bases): return (object,)

timezone = _AutoMock('timezone')

Common Errors

Error / Symptom	Cause	Fix
`TypeError: can't compare offset-naive and offset-aware datetimes`	Mixing aware + naive	Attach tz: `dt.replace(tzinfo=...)` or convert with `astimezone`
`ValueError: time data '...' does not match format '...'`	`strptime` format mismatch	Print both, fix the directive (likely `%M` vs `%m`)
Got month `30`, minute `5`	Swapped `%m` (month) with `%M` (minute)	`%m` month, `%M` minute, `%S` second
`ZoneInfoNotFoundError` on Windows	tzdb missing	`pip install tzdata`
Off-by-one date from `fromtimestamp`	Implicit local conversion	Pass `tz=timezone.utc` explicitly
`strftime` on naive datetime drops `%z`	No tzinfo to format	Make it aware first

1 · The lesson

1. Format Directives

2. Creating Datetimes

3. Parsing Strings

4. Formatting

5. timedelta

6. Timezones (zoneinfo, 3.9+)

Common Patterns

Common Errors

See Also

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