It depends on the woman. Some women don't care when or where you propose to them as long as you do. Usually Valentine's Day is the most romantic time of year. Some women want the special day to remember when there is no holiday or occasion such as Graduation, her birthday, Christmas, etc. You know her best. As long as it's over a romantic dinner then you can't lose. The most romantic time of the year to propose is on Valentines Day. That's when she is going to be so surprised she's not going to expect you to do nothing like that. She probably won't expect nothing at all. So yeah that's the most romantic time of the year. As a woman, I would suggest against Valentine's Day, but that's just me. Think about what kind of girl this is. Does she love to go to the beach in the summer and hate the cold? Then don't propose to her during a snow storm! Is she from an area of the country that has beautiful fall foliage? Is Christmas her favorite holiday? You can make it even more special for her by proposing then. Think about what's important to your girlfriend, and what kinds of weather she likes. Then decide.