I find that synaesthesia definitely gave me a slight advantage in terms of an inbuilt memory device and mental calculator. The true potential of synaesthesia can be seen from the prodigious feats of Daniel Tammet.
I definitely picture time on a visual scale in my mind, with the calendar year appearing as a kind of circular carousel, rotating through the months. On a separate, weekly, scale the weeks connect to each other to form a long, straight ticker-tape which I can just shuffle through.
On a long term scale of years, decades and centuries, the time scale is more of a winding path with various events placed along it. Each century is proportional in length to how well versed I am to the events it holds, so some centuries like 3-8th are really short and others like 19-20th are really long and windy.
When it comes to numbers and letters though, I don't associate them with colours or textures, but rather attribute a distinct personality to each number. I'm not sure if that qualifies as synaesthesia but pretty much every number up to 1000 has a distinct personality and after that it gets a bit hazy, with the numbers taking on a mix of characteristics from their components. The single digit numbers have the more vivid and complex personalities of course, with 5 being humble, trustworthy and simple-minded, 6 is sly abnd yet beautiful, 8 is plain and jealous of 6, 9 is tall, silent, shy and in love with 8, etc... It even works in reverse sometimes, to the extent that I associate people with a particular number.
As for music, I only really associate my most favourite songs with colours, and that's mainly dictated by the predominant hues featured in the corresponding music videos, so my synaesthesia is definitely lacking n that area.