Hello, Norm!
It seems that the experts here at WikiTree and at Quora agree that either tense (past or present) is acceptable, but disagree on which is the preferred. MY personal preference is to use present tense for a timeline, as it makes the timeline "come alive!"
The real issue, as you surmised, is to be consistent throughout the timeline - use either all present tense or all past tense.
Biographies, for the most part, should be past tense; however, for living individuals, some parts of the bio may require present tense (for example, "Lindy Jones currently lives in a white house, though it is not the famous White House in Washington, D. C.").