Timeline on a string

Sitting on top of my jewellery box
Is something very special to me
It's a timeline of memories
Memories on a silver string
Over the years it may lose and gain charms
But the meaning will never change
Its charms gained one by one
For birthdays, Christmas and the start of something new
Its charms shine like stars in the dark lit night
It's too special to wear
But not too special to keep