My second anniversary and a disturbing issue

I have my second wedding anniversary on 16th of February. Few days back, me and DH were discussing about organizing a family lunch on 15th Feb, which happens to be a Sunday. We usually plan such meals for Sundays since it is convenient for both sides [my in-laws and my parents].
Now, a little background, my MIL & FIL (he is no more) got married on 15th Feb. Since last few days, when I am at work and DH works from home, I don't know what transpires between the two, I am told by my DH that we have to cancel the Lunch on 15th Feb since his mom has told him that she can't have celebration that particular day, since she misses her husband badly.
I was totally shocked because no matter how hard I try, i just can't accept this logic. I tried to reason with my DH. He said we can plan it any other day but not on 15th. Now my point is that on 16th, me & DH would take a leave and only the 2 of us would spend time together and 14th would not suit my parents since my mom would have a working half day. Also, organizing a dinner would also not be possible since my brother has a new born baby and he can't leave his wife and child , and my dadi alone at home at night. They can spare some time out for lunch since the baby sitter would be there but since my mom would be at work, the lunch can't be organized.
So we were left with 15th Feb only. My DH feels very very strongly for his mom because after my FIL died a couple of years back, these 2 have been together and have bonded really strong, making me feel like a third party, sometime.
My point here is not that I am dying to organize a lunch, but I am just not able to comprehend my MIL's intentions here. I asked my DH that why 2 years back, on 15th of FEB only you guys arranged Mehndi & sangeet? How could mom be happy that day, 2 years back and the same date brings remorse to her after 2 years [last year my MIL was wil SIL, at the time of my anniversary].
To be honest, in the last few months, the equation between me & DH, me & MIL has improved because all of us are putting our efforts towards accepting each other and ignoring what can't be changed. This has actually brought a lot of piece and harmony in our family life.
This episode has however, again hit me strangely, if not badly. Had it been my FIL's death anniversary, I would have accepted my MIL's logic and DH's blindfold support to her logic, wholeheartedly, but this scenario upsets me. Why cant she understand that me and DH are working and we rarely get days where family get togethers can be organized. Why is she coming up with this issue now when on the same date 2 years back she was in full swing involved in the celebrations.

I know this might be a very trivial thing and I should let it go, not act so self-centered, etc. but still, is my MIL and my DH justified? I have more problem accepting the fact that DH agrees blindly to whatever whim my MIL has without thinking about the grave repurcussions that these whims are imposing on our matrimony?
I look forward to your insights ladies.

 

Yes Guesshoo, I have accepted this thing partially, but not able to let go of it, completely.