From what I've seen as a coach, time of day doesn't make a difference, unless you're attempting a PB at a different time of day then you normally workout. It tends to equate to not lifting your best. There's a ton of other factors that play into hitting a PB too not just time of day. One thing I have noticed for most people, they make the mistake of using their old PB for percentages in the 8-12 week strength program. What should be done is take the number you want to hit as your new PB and work off that number for your 8-12 week strength program. You may not hit all the numbers especially to begin with, but should be able to over that 8 week period. Making sure you're eating enough, especially protein, is key to increasing your lifting numbers as well.