What does "all in a day's work" mean?

Also, all in the day's work.

Expected and normal, as in He said I had to finish these reports by five o'clock—all in the day's work. This phrase is sometimes used as an ironic comment on an unpleasant but not abnormal situation. The expression possibly alludes to the nautical term day's work, defined in 1789 as the reckoning of a ship's course during the 24 hours from noon to noon. [c. 1800]