When two words are practically made into one syllable, a thin space may be put before the apostrophe, except that don’t, can’t, won’t, and shan’t are consolidated. This use of a space serves to distinguish between the possessive in s and the contraction of is.
Where death ’s abroad and sorrow ’s close behind.
4. Figures expressing dates are often abbreviated, but it is not good general practice.
The boys of ’61.
It happened in ’14.
5. The apostrophe is used to form the plural of letters and figures.
Cross your t’s and dot your i’s.
Make 3’s and 5’s more plain.
Except in these cases the apostrophe is not a plural sign and should be so used only when it is intended to reproduce a dialect or colloquialism.
Wrong: All the Collins’s were there.