Send it back to true love

For any day $n$ such that $0< n \leq 12$ , the number of gifts the person in the song receives is

$g = \large \frac {n(n+1)}{2}$

So we need to find

$\large \sum_{n=1}^{12} \frac{n(n+1)}{2}$

$= \large \sum_{n=1}^{12} \frac{n^2 + n }{2}$

$= \large \frac{1}{2} [ \frac{(n)(n+1)(2n+1)}{6} + \frac {n(n+1)}{2} ]$

$= \large \frac{1}{2} [ \frac{(12)(12+1)(2(12)+1)}{6} + \frac {12(12+1)}{2} ]$

$= \large \frac{1}{2} [ \frac{(12)(13)(25)}{6} + \frac {12(13)}{2} ]$

$= \large \frac{1}{2} [ 650 + 78 ]$

$= \large \boxed {364}$ .