The River Of Time

The Boat Of A Million Years, XIV, 2.

Time is like a river. See:

Individuals In The Time Stream

- and:

"...what could be more appropriate for a time travel series? There is real human experience and there is imagined time travel experience and a skilled sf writer blends them together:

"It was a strange thing to meet her at intervals of months which for Havig were hours or days. Each time, she was so dizzyingly grown. In awe he felt a sense of that measureless river which he could swim but on which she could only be carried from darkness to darkness.
-Poul Anderson, There Will Be Time (New York, 1973), IX, p. 98.

"We have already looked at time as a river in the Time Patrol."

-copied from here.

- and rivers are like time:

Time And The River

(The passage about Jack Havig's awesome sense of that measureless river is quoted several times.)

Now Hanno the immortal refers to the River:

"O Hiram, Psammetk, Pytheas, Althea, Athenais-Aliyat, Armand Cardinal Richelieu, Benjamin Franklin, how far has the River borne me from you!" (p. 280)

Characters in different timelines have a lot of common experience.