# How long is a month? **URL:** \ **Category:** Akrasia\ **Created:** [February 15, 2021, 4:23pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013 "2021-02-15T16:23:39Z")\ **Posts on this page:** 11\ **Page:** 1
**Author:** ![gfredericks](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/gfredericks/32/3979_2.png) [@gfredericks](https://forum.beeminder.com/u/gfredericks)\ **Post date:** [February 15, 2021, 4:23pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/1 "2021-02-15T16:23:39Z")
Months (and years) don’t last the same amount of time (neither do days/weeks because of DST, but I think that might be ignorable), so I am just curious how beeminder defines them. Most saliently, if your goal is to do something X times per month, does the slope of the road adjust up/down slightly every month, or is beeminder using a different static definition of “month”? (and if it is, how long _is_ a month? or a year?) I’m just curious, this isn’t impacting usability for me at all. ---
**Author:** ![krugerk](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/krugerk/32/5161_2.png) [@krugerk](https://forum.beeminder.com/u/krugerk)\ **Post date:** [February 15, 2021, 5:00pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/2 "2021-02-15T17:00:35Z")
I doubt it means ‘calendar month’ as in the fluctuating duration of Gregorian calendar months and may be amount desired / 30 to produce a daily rate. The Beeminder tick is daily, afaik. ---
**Author:** ![gfredericks](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/gfredericks/32/3979_2.png) [@gfredericks](https://forum.beeminder.com/u/gfredericks)\ **Post date:** [February 15, 2021, 5:15pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/3 "2021-02-15T17:15:21Z")
So by that theory a beeminder month is exactly 30 days. ---
**Author:** ![howtodowtle](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/howtodowtle/32/2284_2.png) [@howtodowtle](https://forum.beeminder.com/u/howtodowtle)\ **Post date:** [February 16, 2021, 2:11pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/4 "2021-02-16T14:11:45Z")
I’m sure the answer will be posted soon, in the meantime my guess is m\_{b} = \frac{365.24}{12}, i.e. an average year in days, divided into twelve equal-sized beeminder months. 🙂 ---
**Author:** ![gfredericks](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/gfredericks/32/3979_2.png) [@gfredericks](https://forum.beeminder.com/u/gfredericks)\ **Post date:** [February 16, 2021, 2:19pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/5 "2021-02-16T14:19:29Z")
If we’re going to be precise then we should go all the way and use 365.2425. ---
**Author:** ![krugerk](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/krugerk/32/5161_2.png) [@krugerk](https://forum.beeminder.com/u/krugerk)\ **Post date:** [February 16, 2021, 3:00pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/6 "2021-02-16T15:00:22Z")
> shows Do It Yourself or Days In a Year rather, at 365.25. ---
**Author:** ![howtodowtle](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/howtodowtle/32/2284_2.png) [@howtodowtle](https://forum.beeminder.com/u/howtodowtle)\ **Post date:** [February 16, 2021, 5:31pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/7 "2021-02-16T17:31:40Z")
Thank you, I just learnt something from the new. I knew about the 4-year rule and the 100-year rule but had never heard of the 400-year rule. 😲 ---
**Author:** ![philip](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/philip/32/1505_2.png) [@philip](https://forum.beeminder.com/u/philip)\ **Post date:** [February 16, 2021, 6:11pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/8 "2021-02-16T18:11:36Z")
> [@howtodowtle](#): > > I knew about the 4-year rule and the 100-year rule but had never heard of the 400-year rule. 😲 It’s the 400-year rule that made a nonsense of the Y2K panic over leap year calculations. The exception to the exception made the normal rule apply… 😃 ---
**Author:** ![howtodowtle](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/howtodowtle/32/2284_2.png) [@howtodowtle](https://forum.beeminder.com/u/howtodowtle)\ **Post date:** [February 16, 2021, 6:45pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/9 "2021-02-16T18:45:54Z")
I was too young to worry about stuff like this in Y2K. And there’s a high likelihood I’ll be too old in 2400 AD. So I must conclude that my set of leap year rules was sufficient for all practical purposes. 😃 ---
**Author:** ![dreev](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/dreev/32/4311_2.png) [@dreev](https://forum.beeminder.com/u/dreev)\ **Post date:** [February 16, 2021, 9:56pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/10 "2021-02-16T21:56:18Z")
Yeah, 365.25 days is what physicists use, for example in defining a light year, so that’s what we went with! A Beeminder month is 365.25/12 = 30.4375 days. ---
**Author:** ![gfredericks](https://sea1.discourse-cdn.com/flex019/user_avatar/forum.beeminder.com/gfredericks/32/3979_2.png) [@gfredericks](https://forum.beeminder.com/u/gfredericks)\ **Post date:** [February 16, 2021, 10:13pm UTC](https://forum.beeminder.com/t/how-long-is-a-month/9013/11 "2021-02-16T22:13:19Z")
Cool, thanks!