Diaries / Calendars for members

I'm setting up a small gardening community www.naturesdesign.uk (I'd be grateful for any comments!)
And I'd like to let my members start diaries of their gardening activity as they go through the year, and then to refer back in future years. They can do this in threads anyway, but I wondered if there is an add on that would let members set up an actual diary / calendar of their own? That they can also share with other members?
I'm looking for this exact same thing! Anyone out there know where I can download a calendar for my members to use as a personal diary/log?

I was hoping there was one floating around that would allow members to paste links in and do a bit of a write up of their activities.