Python: Dates and time

Many programs require the use of dates and times.

Note: The actual output will change depending on when the underlying document was formatted or re-formatted (and the Python program generated and run).

The earth is divided into many time zones with many variations within time zones, such as "Standard Time" and "Daylight Savings Time".

Since the intended applications for this discussion do not require handling times, time zone issues will be ignored.

Here is a Python program to show how to do basic dates and times.

In the Julian day of the year determination, one needs to decide of one wants a 0 based number or a 1 based number. The following program uses a 0 based number.

Here is the Python code [#1]

import datetime
dashDateFormat1 = "%Y-%m-%d"
dashTimeFormat1 = "%H-%M"
now1 = datetime.datetime.now()
print("Now:")
print("")
year1 = now1.year
print("\tYear is {0:d}".format(year1))
month1 = now1.month
months1 = now1.strftime("%B")
print("\tMonth is {0:d} : \"{1:s}\"".format(month1,months1))
day1 = now1.day
print("\tDay is {0:d}".format(day1))
wday1 = now1.weekday()
wdays1 = now1.strftime("%A")
print("\tDay of week is {0:d} : \"{1:s}\"".format(wday1,wdays1))
julian1 = (datetime.date(year1,month1,day1) - datetime.date(year1,1,1)).days
print("\tJulian day of year is {0:d}".format(julian1))
print("\tHour is {0:d}".format(now1.hour))
print("\tMinute is {0:d}".format(now1.minute))
print("\tSecond is {0:d}".format(now1.second))
dashDate1 = now1.strftime(dashDateFormat1)
dashTime1 = now1.strftime(dashTimeFormat1)
dashDate1 = now1.strftime(dashDateFormat1)
dashDate0 = (now1 - datetime.timedelta(days=1)).strftime(dashDateFormat1)
dashDate2 = (now1 - datetime.timedelta(days=-1)).strftime(dashDateFormat1)
print("")
print("Dates:")
print("")
print("\t{0:s} (yesterday)".format(dashDate0))
print("\t{0:s} (today) at {1:s}".format(dashDate1,dashTime1))
print("\t{0:s} (tomorrow)".format(dashDate2))
print("")
len1 = 5
print("Dates past, present and future:")
print("")
for pos1 in range(-len1,len1+1):
	then1 = now1 - datetime.timedelta(days=-pos1)
	thenDate1 = then1.strftime(dashDateFormat1)
	if pos1 < 0:
		print("\t{0:d}. {1:s}".format(pos1,thenDate1))
	elif pos1 > 0:
		print("\t+{0:d}. {1:s}".format(pos1,thenDate1))
	else:
		print("\t {0:d}. {1:s}".format(pos1,thenDate1))

Here is the output of the Python code.

Now:
	Year is 2021
	Month is 3 : "March"
	Day is 22
	Day of week is 0 : "Monday"
	Julian day of year is 80
	Hour is 9
	Minute is 5
	Second is 59
Dates:
	2021-03-21 (yesterday)
	2021-03-22 (today) at 09-05
	2021-03-23 (tomorrow)
Dates past, present and future:
	-5. 2021-03-17
	-4. 2021-03-18
	-3. 2021-03-19
	-2. 2021-03-20
	-1. 2021-03-21
	 0. 2021-03-22
	+1. 2021-03-23
	+2. 2021-03-24
	+3. 2021-03-25
	+4. 2021-03-26
	+5. 2021-03-27