Tense confusion Wikipedia
In grammar, a tense confusion occurs when a writer shifts from the present tense to the past tense (or vice versa). For example, in the following example, the change from "saw" (past tense) to "is" (present tense) represents a tense confusion:
He saw that she is very tall.
It is important to avoid tense confusions because they hurt reader comprehension. They are a common grammatical error, especially among beginning writers.