夜以继日

夜以繼日
yèyǐjìrì
night and day (idiom); continuous strenuous effort

CEDICT

Entry Composition

=1 夜 yè variant of 夜 yè
=1 夜 yè night
=2 以 yǐ old variant of 以 yǐ
=2 以 yǐ old variant of 以 yǐ
=2 以 yǐ
  1. to use
  2. by means of
  3. according to
  4. in order to
  5. because of
  6. at (a certain date or place)
3 继 jì
  1. to continue
  2. to follow after
  3. to go on with
  4. to succeed
  5. to inherit
  6. then
  7. afterwards
4 日 rì
  1. sun
  2. day
  3. date, day of the month