If you want to approach girls in the daytime make sure you go to a place where girls are not too stressed. I usually approach tourists because they are more open to meet new people. It’s also good for practice.
When you approach women at night they are prepared that guys will hit on them but in the daytime few guys have the guts to approach women. It’s really shows that you are confident to start talking to women during the daytime… the girl can often be more nervous than you are.
Either you go direct saying showing your intentions like “I had to come and say hi to you, I knew I would regret if I didn’t… I am John, what’s your name?”
You can also go indirect by asking the girls for directions, this is good for practice.