and labels every 4 hours. The labels are placed under the major grid
lines as they specify exactly that time.
- --x-grid HOUR:8:DAY:1:DAY:1:0:%A
+ --x-grid HOUR:8:DAY:1:DAY:1:86400:%A
This places grid lines every 8 hours, major grid lines and labels
each day. The labels are placed exactly between two major grid lines