Basic Date and Time Types ใน Python (โมดูล datetime)

โมดูล datetime ให้ Classes สำหรับจัดการ Date/Time: date, time, datetime, timedelta, tzinfo, timezone

import datetime

Class Overview

Constants

• datetime.MINYEAR = 1
• datetime.MAXYEAR = 9999

Date Objects

import datetime as dt

# สร้าง Date
d = dt.date(1998, 9, 5)
print(d)                    # 1998-09-05
print(d.toordinal())        # 729637 (Days since 0001-01-01)
print(d.weekday())          # 5 (Saturday, Mon=0)
print(d.isoweekday())       # 6 (Sat, Mon=1)
print(d.isoformat())        # '1998-09-05'

# Class Methods
today = dt.date.today()
from_ts = dt.date.fromtimestamp(1609459200)  # From Unix Timestamp
from_ord = dt.date.fromordinal(732698)

# Arithmetic
delta = from_ord - d
print(delta)                # 3061 days, 0:00:00
print(type(delta))          # 

Time Objects

t = dt.time(14, 30, 59, 123456)
print(t)                    # 14:30:59.123456
print(t.hour, t.minute, t.second, t.microsecond)

# Replace
t2 = t.replace(hour=15, minute=0)
print(t2)                   # 15:00:59.123456

# ISO Format
print(t.isoformat())        # '14:30:59.123456'
print(dt.time.fromisoformat('14:30:59'))

Datetime Objects

# Current
now = dt.datetime.now()
utc_now = dt.datetime.utcnow()

# Specific
dt1 = dt.datetime(2015, 1, 4)
dt2 = dt.datetime(2017, 8, 15)

print(dt1.weekday())        # 6 (Sunday)
print(dt1.strftime('%A'))   # 'Sunday'

# Parsing
dt3 = dt.datetime.strptime('August-15-2017', '%B-%d-%Y')

# Difference
diff = dt3 - dt1
print(diff)                 # 954 days, 0:00:00
print(diff.total_seconds()) # 82425600.0

strftime / strptime Directives

Timezone Handling (Python 3.9+ ZoneInfo)

from datetime import datetime, timezone, timedelta
from zoneinfo import ZoneInfo  # Python 3.9+

# Fixed Offset
tz = timezone(timedelta(hours=7))
dt_tz = datetime(2024, 1, 15, 14, 30, tzinfo=tz)

# IANA Timezone
dt_bkk = datetime(2024, 1, 15, 14, 30, tzinfo=ZoneInfo('Asia/Bangkok'))
dt_utc = dt_bkk.astimezone(timezone.utc)

print(dt_bkk)   # 2024-01-15 14:30:00+07:00
print(dt_utc)   # 2024-01-15 07:30:00+00:00

Timedelta Operations

td = dt.timedelta(days=7, hours=3, minutes=30)
print(td)                       # 7 days, 3:30:00
print(td.total_seconds())       # 617400.0

# Arithmetic
future = dt.datetime.now() + dt.timedelta(days=30)
past = dt.datetime.now() - dt.timedelta(weeks=2)

Best Practices

• ใช้ datetime.now(timezone.utc) แทน utcnow() (Deprecated 3.12)
• เก็บ UTC ใน Database, แปลง Timezone ตอนแสดงผล
• ใช้ zoneinfo (3.9+) แทน pytz
• Duration ใช้ timedelta, ไม่ใช่ Datetime Diff
• Parsing: fromisoformat() (3.7+) เร็วกว่า strptime