No less a grammar curmudgeon than H. W. Fowler saw nothing wrong with spelling the adverbial expression “some time” as one word, or connecting the words with a hyphen: sometime, some-time.
HOWEVER, Fowler pointed out that convenience favors spelling the adverbial expression as two words in order to keep a distinction between
some time in the sense of “at some time or another,” as in Let’s have lunch together some time,
sometime, meaning “formerly” or “former” as in Mr Jones, sometime Mayor of Cleveland, spoke to journalists.
The distinction continues to be a useful one.