Python – Convert day number to date in particular year

Given day number, convert to date it refers to.

Input : day_num = “339”, year = “2020” 
Output : 12-04-2020 
Explanation : 339th Day of 2020 is 4th December.

Input : day_num = “4”, year = “2020” 
Output : 01-04-2020 
Explanation : 4th Day of 2020 is 4th January. 

Method #1 : Using datetime.strptime()

In this, we get the year string and day number string, and pass to strptime(), converts to the corresponding required date.

Python3

# Python3 code to demonstrate working of
# Convert day number to date in particular year
# Using datetime.strptime()
from datetime import datetime

# initializing day number
day_num = "339"

# print day number
print("The day number : " + str(day_num))

# adjusting day num
day_num.rjust(3 + len(day_num), '0')

# Initialize year
year = "2020"

# converting to date
res = datetime.strptime(year + "-" + day_num, "%Y-%j").strftime("%m-%d-%Y")

# printing result
print("Resolved date : " + str(res))

Output

The day number : 339
Resolved date : 12-04-2020

Method #2 : Using timedelta()

In this, we initialize the date by 1st of January and then add number of days using timedelta(), resultant gives the date required.

Python3

# Python3 code to demonstrate working of
# Convert day number to date in particular year
# Using datetime.strptime()
from datetime import datetime, date, timedelta

# initializing day number
day_num = "339"

# print day number
print("The day number : " + str(day_num))

# adjusting day num
day_num.rjust(3 + len(day_num), '0')

# Initialize year
year = "2020"

# Initializing start date
strt_date = date(int(year), 1, 1)

# converting to date
res_date = strt_date + timedelta(days=int(day_num) - 1)
res = res_date.strftime("%m-%d-%Y")

# printing result
print("Resolved date : " + str(res))

Output

The day number : 339
Resolved date : 12-04-2020