Help with basic table with date & time inputs

I want to do a table with 3 columns for date with time, carbs intake and ketones, if you're familiar with what I'm doing. I'll be using android mobile version to make this so no graphs til later.

So it would be two sets of data I'll be comparing and combining into a graph from the table. I've never done this but I imagine I can unless you tell me different.

So starting off what would be the formula to punch in for the date and l time. I've been using a circular one for simply date in other spreadsheets familiar with that works but if any of you have better ideas I'm open to suggestions and I haven't done anything with exact times so I'll need help with that.

Next will be converting to graphs which I'll worry about later when I'll be able to access the sheet from a desktop version of excel.