Get the Number of Days in a Month Using Ruby

Get the number of days in a month using Ruby
With a one-line function you can retrieve the number of days in a given month. Month must be passed as a number (1 to 12.)
def DaysIn(MonthNum)
  (, 12, 31).to_date << (12 - MonthNum)).day
  1. def DaysIn(MonthNum): This line defines a function named DaysIn that takes one parameter, MonthNum, representing the month number (1 for January, 2 for February, etc.).
  2., 12, 31).to_date << (12 - MonthNum): This line creates a Date object for the last day of the current year (, 12, 31)) and then uses the << operator to subtract months from this date. (12 - MonthNum) calculates how many months to subtract to get to the desired month.
  3. .day: This returns the day of the month, which, since the date has been adjusted to the last day of the desired month, will be the number of days in that month.

However, there’s a more straightforward way to achieve this in Ruby:

def DaysIn(month_num), month_num, -1).day

This revised function directly calculates the last day of the given month by setting the day parameter to -1, which Ruby interprets as the last day of the previous month. Thus, this yields the last day of month_num in the current year. This method is clearer and more idiomatic in Ruby.

Nathan Pakovskie is an esteemed senior developer and educator in the tech community, best known for his contributions to With a passion for coding and a knack for simplifying complex tech concepts, Nathan has authored several popular tutorials on C# programming, ranging from basic operations to advanced coding techniques. His articles, often characterized by clarity and precision, serve as invaluable resources for both novice and experienced programmers. Beyond his technical expertise, Nathan is an advocate for continuous learning and enjoys exploring emerging technologies in AI and software development. When he’s not coding or writing, Nathan engages in mentoring upcoming developers, emphasizing the importance of both technical skills and creative problem-solving in the ever-evolving world of technology. Specialties: C# Programming, Technical Writing, Software Development, AI Technologies, Educational Outreach

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