coextend

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To extend or cause to extend through the same space or duration.

Century Dictionary and Cyclopedia

1. To extend equally; cause to extend through the same space or duration; place so as to coincide or occupy the same extent or space.
2. To reach to or attain the same place, time, or duration: used with with.

Wiktionary

1. v. transitive, intransitive To extend along with another.

GNU Webster's 1913

1. v. To extend through the same space or time with another; to extend to the same degree.