Saturday is the seventh or Sabbath day. That's why you see all the Jews going to the Synagogues on Saturday.
Sunday is the day that Jesus rose from the dead. Christians meet together on the first day of the week to "break bread" and living in observance of the ressurection of Jesus.
e.g. Acts 20:7, 1 Cor 16:2
St. Ignatius says Christians are "no longer observing the Sabbath, but living in the observance of the Lord's Day, on which also Our Life rose again".
Do you think those two verses are good enough for me to claim the money?