Ruby code to get the date of next Monday (or any day of the week)

Question

Given an input of, for example,

day = 'Monday'

how can I calculate the date of the next day?

def date_of_next(day)
  ...
end

Formularize

Answer 1

require 'date'

def date_of_next(day)
  date  = Date.parse(day)
  delta = date > Date.today ? 0 : 7
  date + delta
end

Date.today
#=>#<Date: 2011-10-28 (4911725/2,0,2299161)>
date_of_next "Monday"
#=>#<Date: 2011-10-31 (4911731/2,0,2299161)>
date_of_next "Sunday"
#=>#<Date: 2011-10-30 (4911729/2,0,2299161)>

Lanctot

Date.parse(day) awesome trick... before this answer I didn't know.. +1 – Favata

Answer 2

For anyone like me who came here looking for a solution in Rails to this problem, as of Rails 5.2 there is a much easier method to do this.

For anyone (like the original poster) not specifically using Rails, this functionality is available in the ActiveSupport gem.

To find the next occurring day of a week, we can simply write something like Date.today.next_occurring(:friday).

See the documentation for more details.

Coffman

Answer 3

I know this is an old post, but I came up with a couple of methods to quickly get the previous and next day of the week.

# date is a Date object and day_of_week is 0 to 6 for Sunday to Saturday

require 'Date'

def get_next_day(date, day_of_week)
  date + ((day_of_week - date.wday) % 7)
end

def get_previous_day(date, day_of_week)
  date - ((date.wday - day_of_week) % 7)
end

puts today = Date.today
# 2015-02-24

puts next_friday = get_next_day(today, 5)
# 2015-02-27

puts last_friday = get_previous_day(today, 5)
# 2015-02-20

Tint

in your example you used "5" as the day of the week, but wrote monday as the variable name. I think you meant to use "friday" – Cloudberry

@PETER: Thanks for catching that – Tint

If it's currently Monday, won't get_next_day(date, 1) return the current date? – Bratislava

@MiloP Yes it will. That was the desired behavior for my project. The name of the functions are a little misleading. – Tint

Answer 4

Rails >= 5.2.3

Date.current.next_occurring(:monday)

https://api.rubyonrails.org/classes/DateAndTime/Calculations.html#method-i-next_occurring

Aggressor

Answer 5

For stuff like this I rely on the chronic library.

The Ruby code would be:

def date_of_next(day)
    Chronic.parse("next #{day}")
end

Publicize

Answer 6

If you are using rails you can use Date.today.sunday for Sunday or Date.today.monday for Monday. And then Date.today.sunday - 1.day for Saturday etc.

Credent

Date.today is only available if you are using Rails or have included ActiveSupport. Even then Date.today.monday gives undefined method – Billingsgate

This actually works for me. irb(main):001:0> Date.today.monday => Mon, 17 Aug 2015 – Boner

Date.today.monday should work, but such a method only exists for #monday, not the other days of the week. rubydoc.info/docs/rails/4.0.0/DateAndTime/… – Chungchungking

Keep an eye, this approach doesn't returns you the next monday, but the monday for this week – Jamshedpur

Answer 7

A Rails 4-compatible solution:

(Date.today + 1.week).beginning_of_week(:monday)

where you can provide the day you'd like to find as a symbol argument; the default is :monday.

Note that this will find the next occurrence of the given day - if today is Monday and you're looking for the next Monday, it will return the Monday one week from today.

Some equivalent ways to do it:

1.week.from_now.beginning_of_week(:monday).to_date

1.week.since(Date.today).beginning_of_week(:monday)

(source: https://apidock.com/rails/Date/beginning_of_week/class)

Bratislava

or 1.week.from_now.beginning_of_week(:monday) – Topsyturvy

@Topsyturvy That would return a TimeWithZone, while the OP is looking for a date. 1.week.from_now.beginning_of_week(:monday).to_date would do it. – Bratislava

Answer 8

I know this is a Ruby question, but I think many people using Rails are gonna find this. Many answers use Date.today, which is server time and is usually not a good idea to use if you're on Rails. Recommended to incorporate user's time zone:

DateTime.now.in_time_zone(my_user.time_zone).next_occurring(:monday)

Faris