You mention a date - as I did this morning - that is significant for you, and discover that it has different significance for someone else. 26th April 2009 - the first time I preached at the Gathering Place, turned out fo coincide with the birthday of someone who joined us a couple of years ago.
A few weeks back, I was involved in facilitating some training for peer support volunteers with a cancer charity, and one of the women, in sharing her story recalled the date of her diagnosis - which coincided with my birthday.
On my thirtieth birthday, my then car broke down at Keele services, and the teenage daughter of someone I knew gave birth to a son... I wondered then how his life would pan out (he'll now be 23!) and each birthdya I still do.
Some dates etch themselves onto our memories for one reason or another, and we can be taken by surprise when our "happy" day is someone else's "sad" day, or vice versa.
Perhaps somewhere in this the "rejoice with those who rejoice; weep with those who weep" attitude is important - recognising and holding the tension between what this means for me, and what it means for you; understanding that no one experience or significance is "superior", rather that they are just different.
Many years ago, when I was training for ministry, two couple in the church had sons and daughters-in-law who were waiting the arrival of babies. J arrived first, technically non-viable, but defying predictions and living for a few short hours on a lovely, sunny July day. K arrived a few weeks later, full term, healthy and thriving. The two sets of grandparents shared joy and sorrow, each mindful not to allow their own emotions to dominate or overwhelm the other. I learned a lot from them. I don't recall the birth-and-death date of J, but whenever there is a bright sunny day on July, and I see purple flowers in gardens, I remember, and am grateful.