Or the final second before the new year: new Date ( 2019, 12, 0, 24, 0, - 1 ) // Tue 23:59:59 GMT+0000 (Greenwich Mean Time)Īnd it’s the same behaviour when you mutate a date object - it does the cleverness on write so it reads back normally. The two can be combined to get the last day of the year by asking for the zeroeth day of the thirteenth month (remembering it’s zero-indexed, so month number 12): new Date ( 2019, 12, 0 ) // Tue Dec 31 2019. tDate(0) This works for most dates, but fails if date is already the last day of the month, on a month that has more days than the following month. It works with months too, and across years: new Date ( 2019, 11 ) // Sun Dec 01 2019. Beware of any answers for the last of the month that look like this: var last new Date(date) tMonth(last.getMonth() + 1) // This is the wrong way to do it. new Date ( 2019, 6, - 1 ) // Sat Jun 29 2019. If a negative number is provided for dayValue, the date will be set counting backwards from the last day of the previous month. Obviously zero is the day before the first day of a month?! And zero isn’t a special case, you can continue to count back: new Date ( 2019, 6, 1 ) // Mon Jul 01 2019. const endOfMonth = new Date ( 2019, month + 1, 0 ) // Sun Jun 30 2019.

const startOfMonth = new Date ( 2019, month, 1 ) // Sat Jun 01 2019. Here’s an example: const month = 5 // June. It turns out the way to get the last day of a month is to ask for the day before the first day of the following month! I particularly like that phrasing because it’s both a description for humans and an explanation of the code. Throughout this post remember that in JavaScript a Date’s month number is zero-indexed – so January is month zero and December is month eleven 🙄 – which is something I often forget.

It’s easy to get the first day of a month but what about the last day of a month? Looking on Stack Overflow this is quite a common ask but it’s not something I’d ever encountered and the solution is quite interesting so I thought I’d describe it here. Getting the last day of the month or year in JavaScript

Javascript setdate last day of month