1
general::
Even the lowliest will sometimes come to the fore, as in They may not listen to me now, but just wait, every dog has its day. This proverbial saying alludes to the lowly status dogs once held. [Mid-1500s] Also see HAD ITS DAY.
American Heritage Idioms
2
general::
Phrase(s): Every dog has its day. [and] Every dog has his day.
Prov. Everyone gets a chance eventually. • Don’t worry, you’ll get chosen for the team. Every dog has its day. • You may become famous someday. Every dog has his day.
McGrawhill's American Idioms And Phrasal Verbs