Yes. The dates you specify is simply the time span during which you have to enter and leave Russia. You don't have to travel on these dates. The above said is applicable both for Russian business and tourist visas

A visa to the Russian Federation is a document, permitting stay in Russia for a specific period of time.

Russian visa lists entry/exit dates, your name, passport details, and a purpose of travel. Please note, that your Russian visa is an exit permit just like it's an entry permit: if you lose it or stay over your designated departure date, leaving the country could be more troublesome than entering it.