Python 时间戳处理指南

本文暂提供英文版，中文翻译正在完善中。

Introduction

Python provides two main modules for working with dates and timestamps: datetime for high-level date operations and time for lower-level timestamp operations. Understanding how to properly use timestamps in Python is essential for data processing, API integration, and time-based applications. This guide covers timestamp fundamentals, conversions, timezone handling, and best practices.

Getting Current Timestamp

Using time Module

Copy
PYTHON
1import time
2
3# Get current Unix timestamp (seconds since epoch)
4now_seconds = time.time()
5print(now_seconds)  # e.g., 1704672000.123456
6
7# Get current timestamp as integer
8now_int = int(time.time())
9print(now_int)  # e.g., 1704672000
10
11# Get current time in milliseconds
12now_ms = int(time.time() * 1000)
13print(now_ms)  # e.g., 1704672000123

Using datetime Module

Copy
PYTHON
1from datetime import datetime
2
3# Get current UTC datetime
4now_utc = datetime.utcnow()
5print(now_utc)  # 2024-01-08 00:00:00.123456
6
7# Get current local datetime
8now_local = datetime.now()
9print(now_local)  # 2024-01-07 19:00:00.123456 (if EST)
10
11# Get timestamp from datetime
12timestamp = now_utc.timestamp()
13print(timestamp)  # e.g., 1704672000.123456

Best Practice: Use datetime.utcnow() for UTC timestamps and datetime.now() for local timestamps. Always be explicit about timezone.

Creating Datetime from Timestamp

From Unix Timestamp (Seconds)

Copy
PYTHON
1from datetime import datetime
2
3# Create datetime from Unix timestamp (seconds)
4dt = datetime.fromtimestamp(1704672000)
5print(dt)  # 2024-01-07 19:00:00 (local timezone)
6
7# Create UTC datetime from Unix timestamp
8dt_utc = datetime.utcfromtimestamp(1704672000)
9print(dt_utc)  # 2024-01-08 00:00:00+00:00 (UTC)

From Unix Timestamp (Milliseconds)

Copy
PYTHON
1from datetime import datetime
2
3# Convert milliseconds to datetime
4ts_ms = 1704672000123
5dt = datetime.fromtimestamp(ts_ms / 1000)
6print(dt)  # 2024-01-08 00:00:00.123000

Important: datetime.fromtimestamp() uses local timezone. Use datetime.utcfromtimestamp() for UTC.

From Date Components

Copy
PYTHON
1from datetime import datetime
2
3# Create from year, month, day, hour, minute, second
4dt = datetime(2024, 1, 8, 14, 30, 45)
5print(dt)  # 2024-01-08 14:30:45
6
7# Create date only (time defaults to midnight)
8dt_date = datetime(2024, 1, 8)
9print(dt_date)  # 2024-01-08 00:00:00
10
11# Create time only (date defaults to 1900-01-01)
12from datetime import time
13t = time(14, 30, 45)
14print(t)  # 14:30:45

Python Range: datetime objects can represent years 1 to 9999.

Converting Datetime to Timestamp

Using timestamp() Method

Copy
PYTHON
1from datetime import datetime
2
3# Convert datetime to Unix timestamp (seconds)
4dt = datetime(2024, 1, 8, 14, 30, 45)
5timestamp = dt.timestamp()
6print(timestamp)  # e.g., 1704672654.0
7
8# Convert UTC datetime to timestamp
9dt_utc = datetime(2024, 1, 8, 14, 30, 45, tzinfo=timezone.utc)
10timestamp_utc = dt_utc.timestamp()
11print(timestamp_utc)  # e.g., 1704695045.0

Using calendar.timegm() for UTC

Copy
PYTHON
1import calendar
2from datetime import datetime
3
4# Convert UTC datetime to timestamp (naive datetime assumed UTC)
5dt = datetime(2024, 1, 8, 14, 30, 45)
6timestamp_utc = calendar.timegm(dt.timetuple())
7print(timestamp_utc)  # e.g., 1704695045
8
9# More reliable than timestamp() for UTC naive datetimes

Use Case: calendar.timegm() is useful when working with UTC timestamps from naive datetimes.

Date Arithmetic

Adding and Subtracting Time

Copy
PYTHON
1from datetime import datetime, timedelta
2
3# Add 7 days
4dt = datetime(2024, 1, 8)
5future = dt + timedelta(days=7)
6print(future)  # 2024-01-15 00:00:00
7
8# Subtract 1 hour
9past = dt - timedelta(hours=1)
10print(past)  # 2024-01-07 23:00:00
11
12# Add 2 hours and 30 minutes
13dt = datetime(2024, 1, 8, 10, 0, 0)
14dt = dt + timedelta(hours=2, minutes=30)
15print(dt)  # 2024-01-08 12:30:00
16
17# Add negative timedelta (subtract)
18dt = datetime(2024, 1, 8)
19dt = dt + timedelta(days=-1)
20print(dt)  # 2024-01-07 00:00:00

Calculating Duration

Copy
PYTHON
1from datetime import datetime
2
3# Calculate duration between two datetimes
4dt1 = datetime(2024, 1, 8, 10, 0, 0)
5dt2 = datetime(2024, 1, 8, 18, 0, 0)
6
7duration = dt2 - dt1
8print(duration)  # 8:00:00
9
10# Extract duration components
11print(duration.days)    # 0
12print(duration.seconds)  # 28800 (8 hours)
13print(duration.total_seconds())  # 28800.0
14
15# Calculate in hours
16hours = duration.total_seconds() / 3600
17print(f"Duration: {hours} hours")  # Duration: 8.0 hours

Business Days Calculation

Copy
PYTHON
1from datetime import datetime, timedelta
2
3def add_business_days(start_date, days):
4    """Add business days to a date (excludes weekends)"""
5    result = start_date
6    added_days = 0
7
8    while added_days < days:
9        result += timedelta(days=1)
10        if result.weekday() < 5:  # Monday=0, Friday=4
11            added_days += 1
12
13    return result
14
15# Example
16start = datetime(2024, 1, 8)
17result = add_business_days(start, 5)
18print(result)  # 2024-01-15 (Monday)

Recommendation: Use the python-dateutil library for more advanced business day calculations including holidays.

Formatting Dates

ISO 8601 Format

Copy
PYTHON
1from datetime import datetime
2
3# Format as ISO 8601
4dt = datetime(2024, 1, 8, 14, 30, 45)
5iso_string = dt.isoformat()
6print(iso_string)  # 2024-01-08T14:30:45
7
8# With timezone (using pytz)
9import pytz
10tz = pytz.timezone('America/New_York')
11dt = datetime(2024, 1, 8, 14, 30, 45, tzinfo=tz)
12iso_with_tz = dt.isoformat()
13print(iso_with_tz)  # 2024-01-08T14:30:45-05:00

Custom Formatting with strftime

Copy
PYTHON
1from datetime import datetime
2
3dt = datetime(2024, 1, 8, 14, 30, 45)
4
5# Common format codes
6formats = {
7    'YYYY-MM-DD': dt.strftime('%Y-%m-%d'),  # 2024-01-08
8    'YYYY/MM/DD HH:MM': dt.strftime('%Y/%m/%d %H:%M'),  # 2024/01/08 14:30
9    'Day Month, Year': dt.strftime('%d %B, %Y'),  # 08 January, 2024
10    'Weekday': dt.strftime('%A'),  # Monday
11    'Short Weekday': dt.strftime('%a'),  # Mon
12    'Time': dt.strftime('%H:%M:%S'),  # 14:30:45
13    'AM/PM': dt.strftime('%I:%M %p'),  # 02:30 PM
14}
15
16for name, formatted in formats.items():
17    print(f"{name}: {formatted}")

Format Codes:

Copy
TEXT
1%Y  Year (4 digits)           %m  Month (01-12)
2%y  Year (2 digits)           %d  Day (01-31)
3%B  Month name (January)         %b  Month abbr (Jan)
4%A  Weekday name (Monday)       %a  Weekday abbr (Mon)
5%H  Hour (00-23)             %I  Hour (01-12)
6%M  Minute (00-59)            %S  Second (00-59)
7%p  AM/PM                     %f  Microseconds (000000-999999)

Format for Different Locales

Copy
PYTHON
1from datetime import datetime
2import locale
3
4dt = datetime(2024, 1, 8, 14, 30, 45)
5
6# Set locale
7locale.setlocale(locale.LC_ALL, 'en_US.UTF-8')
8en_format = dt.strftime('%B %d, %Y')  # January 08, 2024
9
10locale.setlocale(locale.LC_ALL, 'fr_FR.UTF-8')
11fr_format = dt.strftime('%d %B %Y')  # 08 janvier 2024
12
13locale.setlocale(locale.LC_ALL, 'zh_CN.UTF-8')
14zh_format = dt.strftime('%Y年%m月%d日')  # 2024年01月08日

Note: locale.setlocale() affects the entire process. Use locale.getlocale() to restore original locale.

Parsing Dates

Parsing ISO 8601 Strings

Copy
PYTHON
1from datetime import datetime
2
3# Parse ISO 8601 string
4iso_string = "2024-01-08T14:30:45"
5dt = datetime.fromisoformat(iso_string)
6print(dt)  # 2024-01-08 14:30:45
7
8# Parse with timezone
9iso_tz_string = "2024-01-08T14:30:45-05:00"
10dt_tz = datetime.fromisoformat(iso_tz_string)
11print(dt_tz)  # 2024-01-08 14:30:45-05:00

Parsing Custom Formats with strptime

Copy
PYTHON
1from datetime import datetime
2
3# Parse custom format
4date_string = "08 January, 2024 14:30:45"
5dt = datetime.strptime(date_string, '%d %B, %Y %H:%M:%S')
6print(dt)  # 2024-01-08 14:30:45
7
8# Parse US format
9us_string = "01/08/2024 2:30 PM"
10dt_us = datetime.strptime(us_string, '%m/%d/%Y %I:%M %p')
11print(dt_us)  # 2024-01-08 14:30:00
12
13# Parse 24-hour format
14eu_string = "08.01.2024 14:30"
15dt_eu = datetime.strptime(eu_string, '%d.%m.%Y %H:%M')
16print(dt_eu)  # 2024-01-08 14:30:00

Format Codes for strptime:

Copy
TEXT
1Same as strftime() format codes:
2  %Y (year), %m (month), %d (day)
3  %H (hour 24), %I (hour 12), %M (minute), %S (second)
4  %p (AM/PM), %f (microseconds)
5  %B (month name), %A (weekday name)

Handling Parse Errors

Copy
PYTHON
1from datetime import datetime
2
3def safe_parse_date(date_string, format_string):
4    """Parse date string with error handling"""
5    try:
6        return datetime.strptime(date_string, format_string)
7    except ValueError as e:
8        print(f"Failed to parse date: {date_string}")
9        print(f"Error: {e}")
10        return None
11
12# Examples
13valid = safe_parse_date("2024-01-08", "%Y-%m-%d")
14invalid = safe_parse_date("invalid date", "%Y-%m-%d")
15
16print(valid)   # 2024-01-08 00:00:00
17print(invalid)  # Failed to parse date: invalid date

Timezone Handling

Using pytz Library

Copy
PYTHON
1from datetime import datetime
2import pytz
3
4# Create datetime with timezone
5tz = pytz.timezone('America/New_York')
6dt_aware = datetime(2024, 1, 8, 14, 30, 45, tzinfo=tz)
7print(dt_aware)  # 2024-01-08 14:30:45-05:00
8
9# Convert between timezones
10tokyo_tz = pytz.timezone('Asia/Tokyo')
11dt_tokyo = dt_aware.astimezone(tokyo_tz)
12print(dt_tokyo)  # 2024-01-09 04:30:45+09:00
13
14# Get current time in specific timezone
15tz = pytz.timezone('Europe/London')
16now_london = datetime.now(tz)
17print(now_london)  # 2024-01-08 00:00:00+00:00

Best Practice: Install pytz with pip install pytz for comprehensive timezone support.

Using zoneinfo (Python 3.9+)

Copy
PYTHON
1from datetime import datetime, timezone
2from zoneinfo import ZoneInfo
3
4# Python 3.9+ built-in timezone support
5tz = ZoneInfo('America/New_York')
6dt_aware = datetime(2024, 1, 8, 14, 30, 45, tzinfo=tz)
7print(dt_aware)  # 2024-01-08 14:30:45-05:00
8
9# Convert to UTC
10dt_utc = dt_aware.astimezone(timezone.utc)
11print(dt_utc)  # 2024-01-08 19:30:45+00:00

Advantage: zoneinfo is built into Python 3.9+, no external dependencies needed.

UTC vs Local Time

Copy
PYTHON
1from datetime import datetime
2
3# Get local time (system timezone)
4dt_local = datetime.now()
5print(f"Local: {dt_local}")
6
7# Get UTC time
8dt_utc = datetime.utcnow()
9print(f"UTC: {dt_utc}")
10
11# Convert local to UTC (requires timezone-aware datetime)
12import pytz
13tz = pytz.timezone('America/New_York')
14dt_aware = datetime.now(tz)
15dt_utc = dt_aware.astimezone(pytz.utc)
16print(f"Converted to UTC: {dt_utc}")

Common Operations

Start/End of Period

Copy
PYTHON
1from datetime import datetime, timedelta
2
3def start_of_day(dt):
4    """Return start of day (midnight)"""
5    return dt.replace(hour=0, minute=0, second=0, microsecond=0)
6
7def end_of_day(dt):
8    """Return end of day (23:59:59.999999)"""
9    return dt.replace(hour=23, minute=59, second=59, microsecond=999999)
10
11def start_of_month(dt):
12    """Return start of month"""
13    return dt.replace(day=1, hour=0, minute=0, second=0, microsecond=0)
14
15def end_of_month(dt):
16    """Return end of month"""
17    if dt.month == 12:
18        return dt.replace(year=dt.year + 1, month=1, day=1) - timedelta(days=1)
19    return dt.replace(month=dt.month + 1, day=1) - timedelta(days=1)
20
21# Examples
22dt = datetime(2024, 1, 15, 14, 30, 45)
23print(start_of_day(dt))    # 2024-01-15 00:00:00
24print(end_of_month(dt))    # 2024-01-31 23:59:59.999999

Age Calculation

Copy
PYTHON
1from datetime import datetime
2
3def calculate_age(birth_date):
4    """Calculate age in years, months, and days"""
5    today = datetime.now()
6    birth = datetime.fromisoformat(birth_date)
7
8    years = today.year - birth.year
9    months = today.month - birth.month
10    days = today.day - birth.day
11
12    # Adjust if birthday hasn't happened yet this year
13    if (months < 0 or (months == 0 and days < 0)):
14        years -= 1
15        months += 12
16
17    return {
18        'years': years,
19        'months': months,
20        'days': days
21    }
22
23# Example
24age = calculate_age('1990-06-15')
25print(f"Age: {age['years']} years, {age['months']} months, {age['days']} days")
26# Age: 33 years, 6 months, -7 days

Countdown Timer

Copy
PYTHON
1from datetime import datetime
2
3def countdown(target_date_str):
4    """Calculate countdown to target date"""
5    target = datetime.fromisoformat(target_date_str)
6    now = datetime.now()
7    diff = target - now
8
9    if diff.total_seconds() <= 0:
10        return {'expired': True, 'text': 'Target date passed'}
11
12    days = diff.days
13    hours = diff.seconds // 3600
14    minutes = (diff.seconds % 3600) // 60
15    seconds = diff.seconds % 60
16
17    return {
18        'expired': False,
19        'text': f"{days} days, {hours} hours, {minutes} minutes, {seconds} seconds",
20        'total_seconds': diff.total_seconds()
21    }
22
23# Example
24result = countdown('2024-12-31T00:00:00')
25print(result['text'])
26# "357 days, 11 hours, 29 minutes, 12 seconds"

Best Practices

Timezone Best Practices

Copy
TEXT
1✅ Always store UTC timestamps in databases
2✅ Convert to local timezone only for display
3✅ Use timezone-aware datetime objects for user-facing times
4✅ Document timezone assumptions in code comments
5✅ Use IANA timezone names (America/New_York, not UTC-5)
6❌ Don't store local timestamps without timezone metadata
7❌ Don't mix UTC and naive datetimes in calculations
8❌ Don't assume server timezone matches user timezone
9❌ Don't use pytz for Python 3.9+ (use zoneinfo instead)

Performance Tips

Copy
TEXT
1✅ Use datetime.timestamp() instead of time.time() for datetime objects
2✅ Cache timezone objects when used repeatedly
3✅ Use datetime.utcnow() for UTC (faster than aware datetimes)
4✅ Use timedelta arithmetic for time calculations (more readable)
5❌ Don't create timezone objects in loops (reuse them)
6❌ Don't call datetime.now() in tight loops (call once and reuse)

Data Integrity

Copy
PYTHON
1from datetime import datetime
2
3def validate_datetime(dt):
4    """Validate datetime object is within reasonable range"""
5    if not isinstance(dt, datetime):
6        return False, "Not a datetime object"
7
8    if dt.year < 1900 or dt.year > 2100:
9        return False, "Year out of reasonable range"
10
11    if dt.month < 1 or dt.month > 12:
12        return False, "Invalid month"
13
14    if dt.day < 1 or dt.day > 31:
15        return False, "Invalid day"
16
17    return True, "Valid"
18
19# Example
20valid = validate_datetime(datetime(2024, 1, 8, 14, 30, 45))
21print(valid)  # (True, "Valid")
22
23invalid = validate_datetime(datetime(2024, 13, 1))
24print(invalid)  # (False, "Invalid month")

Related Tools

• Unix Timestamp Converter - Convert Unix timestamps to dates
• Current Timestamp - Get current timestamp in multiple formats
• Timestamp Format Converter - Convert between timestamp formats
• UTC/Local Converter - Convert between UTC and local time
• Timestamp Validator - Validate timestamp formats and ranges

Additional Resources

• Python datetime Documentation↗
• Python time Module↗
• pytz Library↗
• Python zoneinfo (Python 3.9+)↗
• dateutil Library↗

For production applications with complex timezone or business day requirements, consider using:

• pytz: Legacy but widely supported timezone library
• zoneinfo: Built-in Python 3.9+ (preferred for new code)
• python-dateutil: Advanced date parsing and business day calculations
• pendulum: Pythonic datetime library with better timezone handling

Python's datetime module is sufficient for basic operations, but libraries provide better timezone support and parsing for complex use cases.