None of these is something a fluent speaker would be likely to say. The most likely way to express the idea would be, “February 11 was really hectic, so I had to do a ton of work that day.” “During the day” is usually used when contrasting with “night”. Like, “I work during the day and spend the nights resting.” “In the day” is a somewhat informal way of referring to past times. Like, “In the …

https://ell.stackexchange.com/questions/237624/what-is-the-difference-between-in-the-day-on-the-day-and-during-the-day-i