How to Convert a Date String to Unix Timestamp in Python

Learn Python methods to convert date strings (local time, UTC, ISO 8601) to Unix timestamps, handle timezones, and manage integer vs. float precision for APIs and databases.

A Unix timestamp represents the number of seconds elapsed since the Unix Epoch (January 1, 1970, 00:00:00 UTC). Converting date strings to timestamps is essential for APIs, databases, and time-based calculations.

Converting Local Time Strings

When the date string represents local time, use datetime.timestamp():

from datetime import datetime

date_string = "2023-12-31 23:59:59"
format_string = "%Y-%m-%d %H:%M:%S"

dt = datetime.strptime(date_string, format_string)
timestamp = dt.timestamp()

print(timestamp)  # e.g., 1704067199.0

This method interprets the string as local system time and converts accordingly.

Converting UTC Time Strings

For UTC strings, use calendar.timegm() to avoid timezone confusion:

import calendar
from datetime import datetime

date_string = "2023-01-01 12:00:00"
dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")

timestamp = calendar.timegm(dt.utctimetuple())

print(timestamp)  # 1672574400

Alternatively, create a timezone-aware datetime:

from datetime import datetime, timezone

date_string = "2023-01-01 12:00:00"
dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")
dt_utc = dt.replace(tzinfo=timezone.utc)

timestamp = dt_utc.timestamp()

print(timestamp)  # 1672574400.0

Handling ISO 8601 Format

Python 3.7+ can parse ISO format strings directly:

from datetime import datetime, timezone

iso_string = "2023-06-15T14:30:00+00:00"
dt = datetime.fromisoformat(iso_string)
timestamp = dt.timestamp()

print(timestamp)  # 1686839400.0

iso_utc = "2023-06-15T14:30:00Z"
dt = datetime.fromisoformat(iso_utc.replace("Z", "+00:00"))

Flexible Parsing with dateutil

For varied or human-readable date formats:

pip install python-dateutil

from dateutil import parser

dates = [
    "Jan 1st, 2026 5pm",
    "December 25, 2026",
    "2026/06/15 14:30",
    "15-06-2026",
]

for date_string in dates:
    dt = parser.parse(date_string)
    print(f"{date_string} -> {dt.timestamp()}")

Output:

Jan 1st, 2026 5pm -> 1767286800.0
December 25, 2026 -> 1798156800.0
2026/06/15 14:30 -> 1781533800.0
15-06-2026 -> 1781481600.0

Integer vs Float Timestamps

Some systems use integer timestamps (seconds) while others use milliseconds:

from datetime import datetime

date_string = "2026-06-15 14:30:00"
dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")

timestamp_float = dt.timestamp()

timestamp_int = int(dt.timestamp())

timestamp_ms = int(dt.timestamp() * 1000)

print(f"Seconds (float): {timestamp_float}")
print(f"Seconds (int): {timestamp_int}")
print(f"Milliseconds: {timestamp_ms}")

Output:

Seconds (float): 1781533800.0
Seconds (int): 1781533800
Milliseconds: 1781533800000

Handling Multiple Timezones

Convert strings with timezone information properly:

from datetime import datetime, timezone, timedelta

date_string = "2026-06-15 14:30:00"
offset_hours = -5  # EST

dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")
tz = timezone(timedelta(hours=offset_hours))
dt_aware = dt.replace(tzinfo=tz)

timestamp = dt_aware.timestamp()

print(f"Timestamp: {timestamp}")

Output:

Timestamp: 1781551800.0

Using zoneinfo (Python 3.9+):

from datetime import datetime
from zoneinfo import ZoneInfo

date_string = "2023-06-15 14:30:00"
dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")

dt_ny = dt.replace(tzinfo=ZoneInfo("America/New_York"))
dt_tokyo = dt.replace(tzinfo=ZoneInfo("Asia/Tokyo"))

print(f"Same time, NYC: {dt_ny.timestamp()}")
print(f"Same time, Tokyo: {dt_tokyo.timestamp()}")

Output:

Same time, NYC: 1686853800.0
Same time, Tokyo: 1686807000.0

Complete Conversion Function

A robust function handling various scenarios:

from datetime import datetime, timezone
import calendar
from typing import Optional

def to_timestamp(
    date_string: str,
    format_string: str = "%Y-%m-%d %H:%M:%S",
    assume_utc: bool = False,
    as_milliseconds: bool = False
) -> Optional[float]:
    """
    Convert date string to Unix timestamp.
    
    Args:
        date_string: The date string to convert
        format_string: strptime format pattern
        assume_utc: If True, treat naive datetime as UTC
        as_milliseconds: If True, return milliseconds instead of seconds
    
    Returns:
        Unix timestamp as float, or None if parsing fails
    """
    try:
        dt = datetime.strptime(date_string, format_string)
        
        if assume_utc:
            timestamp = calendar.timegm(dt.utctimetuple())
        else:
            timestamp = dt.timestamp()
        
        if as_milliseconds:
            return timestamp * 1000
        
        return timestamp
        
    except ValueError as e:
        print(f"Parse error: {e}")
        return None

print(to_timestamp("2026-06-15 14:30:00"))
print(to_timestamp("2026-06-15 14:30:00", assume_utc=True))
print(to_timestamp("2026-06-15 14:30:00", as_milliseconds=True))

Output:

1781533800.0
1781533800
1781533800000.0

Common Format Codes

Code	Meaning	Example
`%Y`	4-digit year	2023
`%m`	Month (zero-padded)	06
`%d`	Day (zero-padded)	15
`%H`	Hour (24-hour)	14
`%M`	Minute	30
`%S`	Second	00
`%z`	UTC offset	+0000
`%Z`	Timezone name	UTC

Method Comparison

Method	Timezone Handling	Best For
`dt.timestamp()`	Assumes local time	Local time strings
`calendar.timegm()`	Assumes UTC	UTC time strings
`dt.replace(tzinfo=...)`	Explicit timezone	Known timezone data
`datetime.fromisoformat()`	Parses from string	ISO 8601 format

For consistent results across different environments, prefer timezone-aware datetime objects and explicitly specify whether input strings represent UTC or local time.