The indefinite article "de" in Spanish is analogous to the indefinite article "of" in English.
de means of in spanish
De.
Trienta de octubre translates from Spanish to mean the 30th of October.
El = The De = Of
de que: from what
De = from. Para = to.
Of.
Of where/from where
of the
It means "of" or "from".
IT doesn't mean anything in Spanish. Perhaps you meant:"de mañana", an expression used in Spanish to mean "in the morning"