There are certain instances where out-of-focus tasks complete almost instantly and circumvent their normal progress bar time requirement. A specific case:
When renewing a garden/herb garden/any other street feature, if you start the 50 units of construction tool work, or the 70 units of shovel work and then select a tool in your inventory and repair it while the work is occurring, then the repair will happen almost instantly.
It's obviously pretty uncommon since street items have quite a bit of life, and it's a nice bonus for helping out on projects, but it seems like an unintended behaviour, so I thought I'd point it out.