The Ethiopian Calendar has 12 months of 30 days each, plus five or six additional days (ie a 13th month), which are added at the end of the year.
Okay, so like I said in the opening post, let's use today, February 14, as an example. If someone were to say, "Let's hang out again in one month."
Is "one month" from now, assuming we're counting today:
March 13 (Wednesday), which is 28 days/4 weeks from today, or
March 14 (Thursday), which is the same date as today, or
March 15 (Friday), which is 30 days from today, or
March 16 (Saturday), which is 31 days from today
Let's also assume they don't specify the date. Which do you assume it would be?
This doesn't take leap years into account.
In 400 years there are 97 leap years, 4800 months, so ((365 * 303) + (366 * 97)) / 4800 = 30.436875