by the clock—do smth. paying a lot of attention to the time (so that one is not late):
- There are people who just hate to do anything by the clock.
by the time—at the time that; as soon as:
- Eddie performed with various bands and by the time he was nineteen he left Fort Worth.
Note: The expression does not correlate in meaning with the phrase by the hour—
1. during considerable periods at a time:
- He would argue by the hour, but never for arguing sake.
2. (of wages) paid for the hours given to work:
- The proposal to pay by the hour instead of by the mile would lower the American railroader to the level of his Soviet counterpart.
3. (hyperbolic) very fast:
- Evidence is mounting by the hour that these regulations are being used by the President’s camp to hide behind, and rather ungracefully.