Python standard library: datetime

strptime

import datetime

date_str = '1970-08-28 22:23:24'

dt = datetime.datetime.strptime(date_str, '%Y-%m-%d %H:%M:%S')

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

datetime.toordinal

import datetime

print(datetime.datetime.strptime('0001-01-01', '%Y-%m-%d').toordinal()) #      1

print(datetime.datetime.strptime('1582-10-04', '%Y-%m-%d').toordinal()) # 577725
print(datetime.datetime.strptime('1582-10-05', '%Y-%m-%d').toordinal()) # 577726 - inexisting date
print(datetime.datetime.strptime('1582-10-06', '%Y-%m-%d').toordinal()) # 577727 - inexisting date

print(datetime.datetime.strptime('1582-10-15', '%Y-%m-%d').toordinal()) # 577736 - 1st gregorian day

datetime.date

import datetime;


birthday_ = datetime.date(2014, 8, 28)
print ("Birthday: " + birthday_.strftime("%Y-%m-%d"))


# 

today_     = datetime.date.today()
in_a_week_ = today_ + datetime.timedelta(days = 7)

print ("The date in a week will be " + in_a_week_.strftime("%Y-%m-%d"))

datetime.timedelta

import datetime;

today_    = datetime.date.today()
tomorrow_ = today_ + datetime.timedelta(days = 1)

print ("The date in a week will be " + tomorrow_.strftime("%Y-%m-%d"))

Calculating the Julian Day Number

import datetime
import sqlite3

print ( datetime.date(2025,10,27).toordinal()+1721424.5 )

#
#   Verify with with sqlite3 julianday function:
#
print (sqlite3.connect(':memory:').cursor().execute("select julianday('2025-10-27')").fetchone()[0])

See also