In the USA and Europe, garlic can be planted either in the early spring or late fall / early winter.
Spring PlantingPoor weather conditions often mean that spring planted garlic produces smaller bulbs. In addition the seed garlic must be chilled before planting in order to cause it to break out of its dormancy. That said, spring garlic planting can produce good results in the warmer Southern areas where it is often planted in late February or March. It also removes any possibility of the plant being damaged by the winter cold.
Autumn / Fall PlantingIn more Northerly areas it more common to plant garlic towards the end of the year. In Europe there is a tradition of planting garlic on the shortest day of the year, however this is probably more for symbolic reasons than horticultural ones.
The usual advice to gardeners is to plant fall garlic soon after the first major frost of the year, usually between mid-October and late November depending on your local climate. Garlic is generally winter hardy, however can be damaged if the temperatures are very cold and the snow cover thin. If this is the case, cover the garlic with straw to protect it.
If all is well then the shoots of fall planted garlic should emerge from the ground in early spring. If not then you still have the opportunity to plant a spring crop.