record modification time for each cell in sagews

[haraldschilly]

To augment the notification system, I suggest to record the current time (UTC) as a timestamp for each cell in the sagews. E.g. pseudocode

from time import time
{ ... "mtime" : int(time()) }

At some point later, one could use that information to highlight recent modifications, or filter displayed cells based on time, etc.

[williamstein]

it could instead have the start and stop time, so you also know exactly how long it took to execute...