Time blocks

I work with a time block structure.

Start times of each blocks is outlined below

915, 1115, 315, 515, 715, 915

The 915 one is for check in with team. Q1 block proper.

The 1115 one is the primary Q2 block.

The 315 is the placeholder block. Q1 / Q2 based on realities of the day.

515 block is for my walk. Q2 proper.

715 is my Office block and 915 is Open Q2 block.

315 and 715 blocks are where ad hoc meetings requests get accommodated as need be.

Q1 blocks are for doing things. Q2 blocks for getting things done.

Placeholders blocks are essentially reserved blocks. To allocate as Q1, Q2 as need be.

You would have also noticed all my time blocks start at 15. Any thoughts on why?