How to link to next date (day/month) with date in url?

Question

When displaying entries by date: /blog/2013/09/12 (day) or /blog/2013/09 (month),

1. How can i get the link to the next/previous day or month?
2. More important, when using the channel calendar tag, using the day-path variable in the calendar will show links for days that have entries. When visiting such a link (/blog/2013/09/12), how can i link on that page to the next date that does have entries ?