Block language, for English, is used for captions, titles and newspapers headlines.
Besides articles like "a", "an", and "the" which are always removed, are prepositions like "in", "at", "on", etc liberally dropped as well?
From some school website, I found:
"Available January and June"
It looks like "in" was removed from between "Available" and "January and June".
But you asked if they were liberally dropped in headlines etc. The sentence you have posted does not appear to be a headline or a title. Had it simply said "Class available January and June", then it would be fine and commonly seen in perhaps a college timetable.
You will find a lot of instances where the preposition is dropped before days, months etc.
He was born January 1970.
The sale runs Monday through/to Friday.
I took my exams July 2009.
To me, 1 and 3 are unnatural but I've heard them many times, perhaps mostly in AmE.
1. He was born January 1970.
2. The sale runs Monday through/to Friday.
3. I took my exams July 2009.
Modifying 1 and 3 slightly:
1a. He was born January.
3a. I took my exams July.
Would 1a and 3a, from which year-expressions were removed, still be acceptable?