On the other hand, the preposition “at” is used when it is followed by a specific time (e.g., 12:45), and on certain parts of the day (i.e., noon, night, midnight). Finally, “On” is the preposition used for dates (e.g. June 5) and days of the week. These prepositions can be used in the same sentence, as seen below: More @Wikipedia
Hover over any link to get a description of the article. Please note that search keywords are sometimes hidden within the full article and don't appear in the description or title.