When you get married, a lot of new days by default become important to you. Of course, you have your anniversary, which you should never, never, never forget. Hopefully the day was memorable enough that this will be no problem.
Hopefully her birthday will also not be a problem, because it also needs to be recognized. The ones that are little trickier are the ones coming from your in-laws. It is a good idea in order to build bridges with them, to recognize them on their special days, such as their birthdays. Depending on the size of your in-law family, this could be a difficult task.
One thing that I found to help me is to set reminders on my phone. Nowadays, most phones will do this and will even let you set up the reminder as an annual event. Set a reminder for a day or a few days before the day to remind yourself to give that person a call or to do something nice for them.
After a while, these things will become routine so that you don’t have to rely on something else to remind you. If anything, this simply allows you to show that you take the time out of your busy life to pay attention to other people, which is an excellent way to strengthen your relationship with your wife and her family.