slightly faster to do ... * 86400

No, any good optimizer should optimize away those multiplications (in any language) anyway (so if its done in a loop it shouldn't matter, and if its only done once then it makes too little difference to matter), and its better self-documentation IMHO to leave it as '24*60*60' because those numbers mean something to me, whereas 86400 does not. Someone could inadvertently change it to 84600 and I wouldn't notice the difference until many wrong calculations had been done. In any case, this is a bad place for micro-optimizations...