One of the rules we learned in school was “Day is masculine, but its parts are feminine.” That has been a huge help in remembering the gender of dí­a.

However, it is somewhat humorous to still hear native Spanish speakers say, “Buenas Dí­as.”

Mañana
This can mean tomorrow or morning. Most of the time when it means morning it will be in the phrase “la mañana.”

Tarde / Noche
These are afternoon and night. It is somewhat ambiguous as to when tarde ends and noche begins. This is probably a very regional distinction; however, where we live, 8:00 in the evening is somewhat the separation time. When it gets dark at 6:00 in the afternoon, it is hard to think that the night has not started. Or in the summer it can be well after 9:00 before the sun drops below the horizon. The cut off from one to the other is very flexible.

Remember the rule “Dí­a is masculine, but its parts are feminine.”