Python Date and Time Manipulation Tutorial

This article demonstrates how to work with dates and times in Python using the datetime module, pandas , and dateutil , covering retrieval of the current timestamp, formatting, conversion, indexing, and arithmetic operations.

1. Get the current date and time

Return the current date and time:

from datetime import datetime
print(datetime.now())

Return the current year, month, and day separately:

from datetime import datetime
print(datetime.now().year)
print(datetime.now().month)
print(datetime.now().day)

Return the current weekday (1‑7) and ISO calendar week:

from datetime import datetime
# weekday (Monday=1)
print(datetime.now().weekday() + 1)
# ISO calendar (year, week number, weekday)
print(datetime.now().isocalendar())

2. Format a specific date and time

from datetime import datetime

# Show only the date part
print(datetime.now().date())

# Show only the time part
print(datetime.now().time())

# Custom format using strftime
print(datetime.now().strftime('%Y-%m-%d'))
print(datetime.now().strftime("%Y-%m-%d %H:%M:%S"))

3. Convert between string and datetime

Convert a datetime object to a string:

from datetime import datetime
now = datetime.now()
print(type(str(now)))

Parse a string into a datetime object using dateutil.parser :

from dateutil.parser import parse
str_time = "2020-03-27"
print(type(parse(str_time)))

4. Time indexing

import pandas as pd
import numpy as np
index = pd.DatetimeIndex([
    '2018-01-01','2018-01-02','2018-01-03','2018-01-04','2018-01-05',
    '2018-01-06','2018-01-07','2018-01-08','2018-01-09','2018-01-10'
])

data = pd.DataFrame(np.arange(1,11), columns=['num'], index=index)
print(data)
# Data for the year 2018
print(data["2018"])
# Data for January 2018
print(data["2018-01"])
# Data from 2018-01-01 to 2018-01-05
print(data["2018-01-01":"2018-01-05"])

5. Time arithmetic

Difference between two datetime objects:

from datetime import datetime
cha = datetime(2018,5,21,19,50) - datetime(2018,5,18,20,30)
print(cha)
print(cha.days)      # days component
print(cha.seconds)   # seconds component
print(cha.seconds/3600)  # convert to hours

Time offset using timedelta :

from datetime import timedelta, datetime
date = datetime(2018,5,18,20,32)
# Add one day
print(date + timedelta(days=1))
# Add 60 seconds
print(date + timedelta(seconds=60))
# Subtract one day
print(date - timedelta(days=1))
# Subtract 60 seconds
print(date - timedelta(seconds=60))

Offset using pandas date offsets:

import pandas as pd
from pandas.tseries.offsets import Day, Hour, Minute
from datetime import timedelta, datetime

date = datetime(2018,5,18,20,32)
# Add one day
print(date + Day(1))
# Add one hour
print(date + Hour(1))
# Add ten minutes
print(date + Minute(10))