First off, define the length of your year - how many days or weeks. Decide on the seasons and their durations. Give each month a theme or characteristic. Maybe create some astrological or mythical influences on the calendar. It's all about getting creative and building a coherent system.
You need to start by deciding on the number of months and days in a year. Then, come up with unique names for the months and days. Also, think about special events or festivals for each month.
Well, creating a fictional year calendar involves a lot of imagination. You could base it on a fantasy world's lore or a sci-fi concept. Consider how the planet's rotation and orbit affect the calendar. And don't forget to add cultural and religious aspects that would shape the way people mark time in that fictional setting.