Answer:
I am bought by the yard but worn by the foot. What am I?
I belong to everyone. Sometimes make you happy, sometimes make you sad. I will never end until the day you do. What am I?
I speak without a mouth and hear without ears. I have no body but I come alive with wind. What am I?
I am a shimmering field that reaches far. Yet I have no tracks and am crossed without paths.
I have keys but no locks. I have space but no room. You can enter but can't go outside. What am I?
No matter how little or how much you use me, you change me every month.