Configure SonicWall TZ300 to allow a specific user access only during certain hours

Create a Rule from LAN to WAN for User1 and Schedule this Rule for the specific hours.

allow access for a specific user only for specific hours during the day?

these user created on firewall or there integration between firewall and domain controller ( ldap ) ?
allow access for what ? internet or network recourses ?

Did you check this link from Sonicwall , you can configure schedule access step by step

https://www.sonicwall.com/support/knowledge-base/assigning-schedules-to-user-based-content-filter-cfs-policies/170503810730718/

Thanks Mohammad.
I would like the user to have remote access to their desktop (full access) as they normally do through the VPN but only during specific hours of the day.
I will check the resources. Many thanks. 

Strivoli, la ringrazio.  I will see if there is some easy way of doing this since I am not experienced with this product. 

yes , you can assign schedule for vpn policy 

there is too many predefined schedule , you can use on them or you can create custom schedule fit your business   

There's a Wizard that helps. After the Wizard is finished you can "refine" applying your Schedules.

I am sorry but I don't have experience using this Sonicwall that is why I was looking for specific instructions.