“Ideally, the Easter Vigil is reserved for those who are being baptized but baptized Christians can be received into full communion at any time. Article 387 of the Canadian Rite of Christian Initiation of Adults says of “Reception of Baptized Christians in the full communion of the Catholic Church” This is the liturgical rite by which a person born and baptized in a separated ecclesial Community is received, according to the Latin rite, into the full communion of the Catholic Church. The rite is so arranged that no greater burden than necessary (see Acts 15:28) is required for the establisment of communion and unity.”
I’m away from home on vacation and thus without access to my RCIA manual but I know from memory that the US version says pretty much, if not exactly, the same thing. I assume then that the December date you mention is only for those who have already been baptized.
The baptism of catechumens (those not yet baptized) is to take place at the Easter vigil and, as I recall, the Rite stipulates that they are to receive First Eucharist and also Confirmation at this time.
And not to worry, receiving the Eucharist for the first time will always be a very special and most memorable occasion for you, whenever it occurs. God bless.