C-Letter Sayings  |  Common Idioms and Phrases  - Their Definitions and Origins
Note: There are times when the origins of phrases are not known. So in those cases, what's usually provided on a saying's page are the popular or plausible theories that are around that talk about how the phrase may have originated. Or if not that, then I'll usually try to mention the earliest known quote of an expression being used in writing. These quotes come from old newspapers, poems, or books most of the time, and are meant to give you an idea on how far back in history an expression goes. So, for example, if I quote a book from the year 1809 because it uses a certain phrase, then it's at least that old.
KnowYourPhrase.com - Common Idioms, Their Meanings and Origins
The earliest that I could find this phrase in writing with the similar wording that it has today is from 
a book called Once A Week, 1872:

    "A correspondent of the same paper, who signs himself 'Octogenarian,' raised the question 
     of the date when 'There's no use crying over spilt milk' first came into proverbial use."

This expression was already a known saying at that time, so it obviously must be older, and indeed it is. There's a book by Hannah Maria Jones called Katharine Bereford; or, The shade and sunshine of woman's life, 1852, and there's a part from it that reads:

    "But it's no use fretting over shed milk."

Apparently, though, the saying is even older. It's said that James Howell, a historian and writer, used the phrase in a book called called Paramoigraphy (Proverbs), 1659:

    "No weeping for shed milk."

This would make the phrase at least over 350 years old.
My kids were upset because they had burnt their toast, but I told them that it's no use crying over spilt milk and to just make some more.

* Bill's car was heavily damaged in an accident earlier and was no longer functional. He was angry about what had happened, but he soon realized that there was no point in crying over spilled milk.

C - a list of sayings.
Phrases and Idioms
Being upset over something that has already happened and cannot be changed.

Usually this phrase is said as "it's no use crying over spilt milk," which means that getting upset over certain things, like spilled milk, is not going to fix it. 
The origin of the idiom 'crying over spilled milk.'