I suspect you might find a laptop very useful since you will find it much more convenient for those times when you need to do more than just a little bit of date entry.
I do not use a specific app that I can recommend for everything but you might be surprised at how well the info from phone and laptop can be integrated.
In fact, I believe the iPhone in particular can share info with an Apple laptop very easily. I am considering moving from Android to iPhone right now.
Hopefully some iPhone users out there will have some specific software recommendations. I will be equally interested in what they have to say.