Python timestamp to datetime and vice-versa

1. What is a Timestamp

A timestamp represents time as the number of seconds since January 1, 1970 (Unix Epoch).

import time

timestamp = time.time()
print(timestamp)  # e.g. 1732452305.4829

It is commonly used in databases, APIs, and distributed systems.

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2. Convert Timestamp → datetime (Local Time)

from datetime import datetime

timestamp = 1732452305
dt = datetime.fromtimestamp(timestamp)

print(dt)

Returns a readable local datetime object.

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3. Convert Timestamp → UTC datetime

from datetime import datetime

timestamp = 1732452305
utc_dt = datetime.utcfromtimestamp(timestamp)

print(utc_dt)

Ensures consistency across global systems.

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4. Convert datetime → Timestamp

from datetime import datetime

dt = datetime.now()
timestamp = dt.timestamp()

print(timestamp)

Transforms a datetime object into Unix epoch seconds.

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5. Timestamp Conversion with Formatting

from datetime import datetime

timestamp = 1732452305
dt = datetime.fromtimestamp(timestamp)

print(dt.strftime("%Y-%m-%d %H:%M:%S"))

Useful for human-readable logs and reports.

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6. Using time Module for Conversion

import time

timestamp = 1732452305
readable = time.ctime(timestamp)

print(readable)

Generates formatted string without datetime objects.

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7. Convert UTC Timestamp to Local Timezone

from datetime import datetime
from zoneinfo import ZoneInfo

timestamp = 1732452305

utc = datetime.fromtimestamp(timestamp, ZoneInfo("UTC"))
local = utc.astimezone(ZoneInfo("Asia/Kolkata"))

print("UTC:", utc)
print("Local:", local)

Critical for timezone-aware applications.

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8. Convert datetime String → Timestamp

from datetime import datetime

date_string = "2025-11-24 14:30:00"
dt = datetime.strptime(date_string, "%Y-%m-%d %H:%M:%S")
timestamp = dt.timestamp()

print(timestamp)

Common in API and log file processing.

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9. Millisecond Timestamp Handling

from datetime import datetime

ms_timestamp = 1732452305482  # milliseconds
dt = datetime.fromtimestamp(ms_timestamp / 1000)

print(dt)

Required for JavaScript and some REST APIs.

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10. Enterprise Example: Database Time Normalization

from datetime import datetime

def normalize_timestamp(input_value):
    if isinstance(input_value, (int, float)):
        return datetime.fromtimestamp(input_value)
    elif isinstance(input_value, str):
        dt = datetime.strptime(input_value, "%Y-%m-%d %H:%M:%S")
        return dt.timestamp()

print(normalize_timestamp(1732452305))
print(normalize_timestamp("2025-11-24 14:30:00"))

Standard pattern for system-wide time normalization.

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Conversion Summary

Operation	Method
Timestamp → Local datetime	datetime.fromtimestamp()
Timestamp → UTC datetime	datetime.utcfromtimestamp()
datetime → Timestamp	datetime.timestamp()
Timestamp → String	time.ctime()
String → Timestamp	datetime.strptime().timestamp()

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Best Practices

• Store timestamps in UTC internally

• Convert to local timezone only for presentation

• Prefer datetime objects for logic

• Avoid mixing timestamps and formatted strings directly

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Common Pitfalls

• Forgetting timezone awareness

• Using milliseconds instead of seconds

• Misinterpreting UTC vs local time

• Formatting before conversion

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