Custom character translation with chartr function, example:
chartr("OIZEASGTC", "01234567(" , toupper(month.name))
# [1] "J4NU4RY" "F3BRU4RY" "M4R(H" "4PR1L" "M4Y" "JUN3" "JULY"
# [8] "4U6U57" "53P73MB3R" "0(70B3R" "N0V3MB3R" "D3(3MB3R"