D3 -得到当前时间，减去2小时

I'm trying to create two variables in d3, one that is the current hour & minute (in 00:00 format) and one that is simply the current time with the hour value subtracted by two. So, for instance: current time is 15:38, the other variable would be calculated to be 13:38. I'm trying to create two variables in d3, one t