The modern-day rendition of this proverb would be: A gloomy morning can turn into a clear day.
It means that even the worst of situations can turn around into good ones as time passes. It can be used to encourage someone to stay positive in the face of difficulty and to have faith that things will get better.
The proverb has been in use since at least the 16th century and originates from a collection of proverbs compiled by John Heywood in 1546.