"Es importante usar el mismo calendario."
Translation:It is important to use the same calendar.
A good sentence to know if I meet someone who still uses the Julian calendar.
...I use four calendars, currently. And I just was gifted another one. I DISAGREE!
It isn't necessary to use a preposition here, either after 'importante', or before 'usar'.
If you follow 'es importante' with 'que', then you would use the subjunctive, but you can use an infinitive instead: 'usar'.
I agree. one would assume that the targets of the statement would have the same "calendar - the only differences I can see is if one starts its week on Monday and another on Sunday.
The difference is small and they're often interchanged.
Utilizar means that you're using a tool to achieve some goal or have a certain effect. So you're using an object for something. Like using the same calendars to organise a schedule.
Usar on the other hand doesn't have a certain goal implied (or rather, the goal is not important). You're just employing the object's service. It's important that we use the same calendars so we won't run into trouble down the line.
Upon writing this, it seems like it's the same difference as between "utilise" and "use" in English if I'm not mistaken.
The word 'to' of the English infinitive 'to use' is included in the Spanish infinitive 'usar'.