Since a year has 365 days, if Gavin has been having 4 dreams every day for a year now, he has had 4*365 = <<4*365=1460>>1460 dreams this year.
Gavin had twice as many dreams last as he had this year, meaning he had 2*1460 = <<2*1460=2920>>2920 dreams last year.
The total number of dreams he has had in the two years is 2920+1460=<<2920+1460=4380>>4380 dreams.
#### 4380