People who want to ride find the time to do so. I wake up at 5-5:30am on most weekends to get in at least 4 hours of riding. If I'm really short on time, I'll go to prospect park and do laps. If I'm really, really short on time I'll just hook the bike up to the trainer and tell people not to bother me for 20-30mins. Just keep your kit/gear ready all the time so you can grab your stuff and go.
Not to mention picking up takeout dinner, going to the grocery or deli, etc. While a 15 minute round trip isn't ideal, any riding is better than not riding. Commuting is also great saddle time.
I'm with DSchlichting. As long as the roads are clear of nasty winter salt/sand/mush I suit up in cold weather gear and go. BTW, "cold weather gear" before I got into lycra and roadie clothes was long johns under my jeans, 2 pairs of socks, winter gloves, and an extra wool sweater under a windproof jacket. For the head, a winter beanie that covers ears and a wool scarf that you can wrap your face with works great.
You'll be surprised at how much cold you can take. Conversely I have a much lower tolerance for riding during the summer heat.