Nope. For most people who menstruate, they’re about every 28 days, but there’s a lot of factors involved. Stress during different phases of your cycle can make your period come either early or late. Some people have wildly irregular periods and can go months without a period, some people have cycle lengths that vary more than the general average of 9 days (so maybe one cycle is 29 days, then the next is 38, then the next is 20.) There’s a lot of variation, some of which is benign, some of which can be a symptom of an underlying condition that can be debilitating or dangerous.
But it’s called “that time of the month” because, like the full moon, there’s usually about one a month, and then once in a blue moon, there’s two.
(Also, the length of months hasn’t always been standardizes in the same way. How different cultures throughout history have broken down and do still break down the year into different intervals is fascinating. For example, some calendars will break the year down by lunar cycles – the term “month” is a cognate of “moon” – and end the year after 12 lunar cycles, while a solar year will end the year after a full revolution of the earth around the sun and break the months down into twelve months around that without consideration for the phases of the moon, while lunisolar calendars will try to reconcile the two by having lunar months and throwing an extra month in every few years to keep things in sync with the sun. You can read more about it here: https://en.wikipedia.org/wiki/List_of_calendars )
TL;DR: No, it’s not exactly once a month. It’s just roughly once a month for most people most of the time, and casual language is imprecise, so it gets called that time of the month.
Nope. For most people who menstruate, they’re about every 28 days, but there’s a lot of factors involved. Stress during different phases of your cycle can make your period come either early or late. Some people have wildly irregular periods and can go months without a period, some people have cycle lengths that vary more than the general average of 9 days (so maybe one cycle is 29 days, then the next is 38, then the next is 20.) There’s a lot of variation, some of which is benign, some of which can be a symptom of an underlying condition that can be debilitating or dangerous.
But it’s called “that time of the month” because, like the full moon, there’s usually about one a month, and then once in a blue moon, there’s two.
(Also, the length of months hasn’t always been standardizes in the same way. How different cultures throughout history have broken down and do still break down the year into different intervals is fascinating. For example, some calendars will break the year down by lunar cycles – the term “month” is a cognate of “moon” – and end the year after 12 lunar cycles, while a solar year will end the year after a full revolution of the earth around the sun and break the months down into twelve months around that without consideration for the phases of the moon, while lunisolar calendars will try to reconcile the two by having lunar months and throwing an extra month in every few years to keep things in sync with the sun. You can read more about it here: https://en.wikipedia.org/wiki/List_of_calendars )
TL;DR: No, it’s not exactly once a month. It’s just roughly once a month for most people most of the time, and casual language is imprecise, so it gets called that time of the month.