Usage and Grammar

Q. I’m unable to find in CMOS, 17th ed., whether the following sentence is acceptable or needs to be rewritten, as it has both a past and future time but only a future verb: Three main planets have, or soon will, change to new signs.

A. It needs to be rewritten, because if you remove the part that is made parenthetical by commas (“or soon will”), the part that remains (“have change to new signs”) doesn’t work. Try this: Three main planets have changed, or soon will change, to new signs.