I have to say, I can't believe there are so many posters who are basically suggesting that you don't ask your husband about his day! My mother is a therapist, and she was always able to talk about her day and NEVER divulged anything that would have violated confidentiality. Lots of stuff happens in a day. I don't know if you're a SAHM, but I know that when I'm home all the time with the kids (like summer vacation) I can't wait to talk about something "adult." He probably is tired, but that doesn't mean that you can't converse!
If you're just doing it to be polite, then don't push it, because it doesn't seem like something very important to your husband. But if you're hungry for a little conversation, clue him in. Tell him sometime, in a non-confrontational way, that you really would like to talk to him a little more when he gets home from work, and you'd appreciate it if he could make little mental notes of things to tell you when he gets home. Say that you're going to do the same. It could be really cute and romantic. You know, if you ask him in advance, he might say something like "walking in to the office, I noticed that the apple tree was in bloom, and I couldn't believe we were so far into fall!" Nothing exceptional, and he probably wouldn't have mentioned it, except that you asked him to. And you do the same. It's a nice way not only to start conversations (oh, should we go apple picking this year?) but to think of each other during the day. Seriously, there's no breech of confidentiality for your husband to mention that one of his unnamed patients had on polka-dot socks that made him think of you.
Good luck!