"This is the first day of March."
Translation:Ini hari pertama bulan Maret.
Pertama = First, Satu = one, Do you have an example of how Satu has been used as first? I can't think of one off hand. Interesting words come from Satu, like the verbs Bersatu (intransitive verb) = "Being one...i.e. United", or the transitive form Menyatu = "Merge or Fuse into one", Satuan (noun) = Unit, Persatuan (noun) = Unity/Association/coalition, Kesatuan = unity/entity etc. From Pertama you can double it to Pertama-tama and get "First of all"....cool words!