Please, speak to your parish office about this.
I work in a parish office. The priest has so much on his mind, we the support staff have responsibilities. One of those is keeping our parishioners informed. Here is what would have happened if you were our parishioner:
For 3 weeks ahead of time there has been a prominent article in the bulletin explaining the two Obligations and the importance of this and Mass times. Same goes for the recording if you call the Parish for Mass times.
Various reminders, articles, etc have been on our Facebook page in the week leading up to a HDO. Same for our website. Also for our customizable front page of
FORMED.org
The sign outside the Church has had the HDO Mass Times listed for at least a week, it is prominent and faces a main “drag” road in town.
The “Liturgy of the Bulletin” announcements have been reminding everyone at Mass for the past couple of weeks.
On the evening prior to the Vigil, you receive either a phone call, a text or an email reminding you of the HDO (you have selected which or all of these methods as reminders).
This also happens for important events like the Our Lady of Guadalupe celebration or the Advent/Lenten communal penance services.
We know that this is part of our job, it is our responsibility and our JOY to help remind people. This world is a very loud and busy place, our parishioners depend on us to help them remember. My husband was in ICU at a hospital an hour away and I took one day to come back to the office to pay some personal bills and do all of the reminders for Immaculate Conception, that is how important my duties are.
Your parish may not know how to schedule advance posts on Facebook or that there are effective reminder services available. PM me and I will give you vendor names and what the pricing is.
I am very blessed, but life is hard and I tend to go through it on autopilot with my head in the clouds. If it’s Monday, I do X and if it’s Tuesday, I do Y and so on. I missed our staff meeting last week because it was on a different day than usual 
Seriously, I need a mobile Alexa to follow me around all day, spouting reminders…
