Syncing Outlook calendar to Yahoo clendar

Has anyone found a good, reliable way to sync outlook calendar events to a yahoo calendar. I travel for work and my MIL uses the calendar to know which weeks i'm out and when she'll have to babysit our child. Since we both have yahoo accounts, that was the easiest method.

However, i haven't been able to find a solution that meets my needs. So far, i've seen these options which don't really do it.

1. Export outlook calendar > This doesn't work because my calendar isn't static. it changes all the time with work trips

2. Sync the Outlook account real time > i've seen this video on how to sync the 2 but because i have several projects for work with large teams, i get calendar invites to a bunch of things they aren't interested in. I suspect it will clutter the yahoo calendar.

3. IFTTT > I haven't found a good IFTTT that will do Outlook to yahoo. Only outlook to gmail.

Does anyone have any other suggestions?