Knowing the best time to do spellwork can be just as important as how you do the spell itself. Of course, it’s not set in stone that you must do your spell only at the prescribed moment. It’s just one more way to add the right sort of energy to your purpose.
Days of the Week
This is my personal tendency. I find that getting the most appropriate day of the week to be the easiest in my somewhat hectic schedule. Just each day of the week is named for either a planet or a Deity, each day is associated with various areas for spellwork. For example, Friday is linked to the planet Venus, and is the perfect day for spells of a romantic or passionate nature.
Phases of the Moon
I think more people use the lunar cycles in their spellwork than any other timing strategy. While I do agree that the moon phases are not as man-made as the 7-day week, I just can’t always make my schedule fit to a 21-day lunar cycle. Most people use the main four phases: new moon, waxing, full and waning. Most calendars indicate the moon phases. Doing an outdoor ritual under the full moon can be quite moving, if nothing else.
I’ve not dabbled in this yet, but I felt I should provide a bit of info on this magickal timetable as well. Calculating the planetary hours of the day is a wee bit more complicated than looking at a calendar and seeing what day it is. Each day is broken down into 24 Hours, with each Hour being ruled by a planet. The chart of hours starts at sunrise, which means it’s a little different each day, as the seasons change. You’ll need to do a bit more research on the details, but basically it means that certain times of the day are better suited to certain kinds of spells. You can read more about this at Llewellyn.
I do like to use seasonal energy in ritual, but it’s not all that practical if you have a pressing need, and the right season is 6 months away. Rather than doing spellwork in relation to your immediate circumstances, try to maybe take advantage of the season at hand to work on some underlying aspect of your life.