Karen: So, you're doing yoga now, and what else?
Naomi: Well, I'm taking a cooking class and teaching English to private students. Today was a little crazy because I had to schedule private students in between my own classes. Remember, I'm finishing my Master's degree too.
Karen: Wow, Naomi! How do you do it?
Naomi: Oh, it's nothing! All in a day's work!
Tom: So, do you have any plans for the weekend?
April: Yes, I do! I'm going to have some friends over and we're going to barbecue...! How 'bout you?
Tom: Nice! Yes, I'm going out of town, but first I have to finish my reports. They're due by 5.
April: All in a day's work, right Tom?
Tom: Yup! Exactly.
Meaning: nothing special, expected and normal
In Example 1, Naomi is used to having a busy schedule, so doing all these things is normal for her!
In Example 2, Tom has to finish his reports before he can leave for the weekend and April is assuring him that it's expected. Sometimes we use "all in a day's work" as an ironic comment when something is unpleasant, but a normal situation.
The idiom "all in a day's work" was taken from Unit 5 (At the Beach) in LSI's textbook Speaking Transitions for Level 4 Listening/Speaking classes.