While the feast of St. Nicholas is on December 6, families can move their celebration to when it's most convenient.
Family life can be messy at times, and it’s possible that the celebration of St. Nicholas on December 6 could throw a wrench into your weekly plans.
A purist would likely say that St. Nicholas must be celebrated on December 6, but in reality, there is more flexibility that even the Church recognizes.
For example, when a parish has a patronal feast during the week, it is permissible to move that feast to the nearest Sunday.
The parish could be named after St. Maximilian Kolbe, and instead of celebrating his feast on a Monday, or a Wednesday, the pastor can move it to the closest Sunday.
Families are their own “domestic churches” and parents as leaders of these “churches” can imitate the parish in this regard.
Basically, if you feel the need to move the custom of leaving out shoes for St. Nicholas a day early, you can do that.
The whole point of these feasts are to honor God and remember the saints who strove to imitate Jesus Christ. The exact date isn’t as important as your faith-filled remembrance.