Could these two pairs of ideas be combined into a compound sentence-The days became longer The children could play outside later?

Here are a couple of ways to combine those two ideas into a compound sentence:

Option 1 (using a coordinating conjunction):

* The days became longer, and the children could play outside later.

Option 2 (using a semicolon):

* The days became longer; the children could play outside later.

Both options express the same relationship between the two ideas (that one event led to the other), but they use different punctuation and conjunctions. Choose whichever option sounds best to you.