We managed to plan everything in about 4 months, what could possibly take a year to prepare?
For starters, our parish church got booked up with weddings quite far in advance, so if we wanted our wedding in the fall or spring when it was not boiling hot and not snowing, we needed to reserve the church about a year in advance. We also had to do the prep with the priest and submit some kind of baptismal paperwork.
Then we had to make preparations for a reception (finding and getting a venue same day as wedding), the meal at the reception, my dress, a cake, flowers, other niceties I wanted (like I made some of my own accessories which meant I had to get materials and spend time making the items), musicians for the Mass and the reception, choose and reserve the photographer for engagement and wedding photos, run the engagement announcement (with engagement photo) in the paper, making sure people were free to be in our wedding, print and send wedding announcements by mail (no Internet then), relatives and friends had to make travel plans, get our Pre-Cana requirements done, a whole host of things.
My husband and I both worked all week and he was frequently getting sent on business trips and I didn’t have anyone else to help me (my mom wasn’t much help), and also all the vendors we were using for cakes and flowers and music and reception etc had many other clients and needed to incorporate us in their planning schedules and meet with us about what was needed. We ended up spending almost every weekend for some months tending to wedding stuff. On the weekends he was away on assignment I was tending to stuff I could do on my own.
My parents planned their wedding in about 6 months but my mother had older siblings helping her, wore a dress she bought off some rack and they had their reception in her parents’ home with family cooking the food. While this was nice for their situation, it was not what I wanted, nor did it work for me as I had no family except my mother who like I said was for various reasons not super helpful.
I would note we had a pretty small wedding with only about 35 guests. If it had been bigger it would have added to the planning complications.
We chose to delay our honeymoon for about 2 years after the wedding, but if a couple wanted to plan their trip for right after the wedding, that would mean more reservations and such needed to be made and paid well in advance, and vacation time from work arranged, etc.