When building a world, one thing to remember is a calendar. This is more important for novels that span several months or years than it is for short stories or novels that take place over a short period of time. You'll also want to decide if there is one general calendar, or if it is different for some cultures.
While creating a calendar, there are questions to ask yourself (or your muse).
Does your world follow Earth's seasons? Spring is followed by Summer, then Autumn, Winter. Or do special conditions create a world or area with one season all year? If you deviate from the logical order of seasons, you want to have a good explanation for it. Don't try to stretch your reader's disbelief too far without reason.
How long is a year? Is it designated by the planet's cycle around the sun, or some other annual event? Or perhaps you have an underground civilization that has need to measure time by other means.
How do they measure the passage of time?
Once your general calendar is set, you can give your character's birth dates, plan future events, create holidays, and make a timeline.
I think every world needs a minimum of two holidays. People need days of rest, celebration, or remembrance. Here are some ideas to create holidays around:
Seasonal – planting, harvest, winter and summer solstice
Events – celebrate or remember a figure's birth or death, freedom from oppression, founding of a culture or city
Other – festival celebrating everyone growing a year older, governmental traditions, individual birthdays, courtship, etc.
For an example, here is the calendar for the realm of Dashevona in the world created for my own work in progress.
There are 14 Moons (months) in a year. 392 days in a year. The year begins with Spring. Each Moon begins with the full moon. Each phase of the moon marks the beginning of a new week and also signals a day of rest. There are four major holidays (listed below), with smaller traditions and rituals for each of the other Moons.
Flower Moon – Flower Fair: celebration of mothers and new life
Festival Moon – Earth Festival: honor Mother Earth, marriage, and change
Blood Moon – The Harvest and the Hunt: food gathered and prepared for winter
Frozen Moon – Winter Feast: large feast in central lodge, with plenty of dancing to keep warm
Good luck and have fun designing your own calendars. One of the best things about writing fantasy is being a god or goddess, having complete control over the creation of a world.
Mary W. Jensen is an author on http://www.Writing.Com/ which is a site for Creative Writing . She is an editor for the Writing.com Fantasy newsletter, and the cofounder of an offline writing group. Mary is writing a fantasy novel, Emergence of the Fey