Calendar entries made on iphone, don't sync to iPad and iCloud

iPad 1, iPhone 4, iCloud on my PC

I want iPhone calendar entries to sync to my iPad and iCloud . . . . not happening!

1) Entries made on iPhone 4 don't sync to iPad or iCloud

2) Entries made on iCloud do sync to iPhone and iPad

3) Entries made on iPad do sync to iPhone and iCloud

I've lived with this issue a long time. I make lots of calendar entries on my iPhone when I'm out and about, then have to enter them again later on my iPad or iCloud. In fact lately I've started scribling them down on a piece of paper instead. If you help me solve this problem you will be my hero :-) - Thanks, IM 😟