# In 上旬・中旬・下旬, why is 上 the start and 下 the end of the month?

I understand that 上旬 means the first 10 days of the month, and that 下旬 means the last (approximately) 10 days of the month. However, I would like to understand the underlying logic for the choice of 上 and 下 for the beginning and end (respectively) of the month.

After all, the later days of the month have higher numbers (21 22 23 etc), so isn't it counter-intuitive that they labeled with 下? There must be a different logical interpretation...

• Does it really require a leap in logic? My calendars have the start of the month on the top. – Leebo Sep 5 '18 at 0:37
• If that's really all there is to it, then that would answer my question! – Nicolas Louis Guillemot Sep 5 '18 at 0:41
• I don't know if there is a clear connection or not, but I explained this for myself by comparing it to vertical writing. You write from top to bottom, so 上 comes before 下 In Japanese. – kuchitsu Sep 5 '18 at 11:01
• Consider also the English phrase, "let's start from the top..." – Eiríkr Útlendi Sep 5 '18 at 16:39