Graph: how to select specific times of day?

Hi, I’m trying to display my pressure readings over a week at specific times of each day (0100, 0700, 1300, and 1900). I’ve looked at transformations and can’t find a suitable one. For example, my attempt to set a query failed when I tried to retrieve mean of the several pressure values taken between 0059AM and 0101AM:

"SELECT mean("value") FROM "PressFlt" WHERE ("time" > 0059 AND "time" < 0101) AND time >= now() - 7d"

I’m querying an influxdb database.
Ultimately I would like to have Grafana draw a graph with four pressure readings from each day at the specific times of day of 0100h, 0700h, 1300h, 1900h. I take pressure readings every 30s and display them on already in Grafana.
(FYI, identifying changes in these readings taken at those times removes the diurnal variation from the changes in the atmospheric pressure - those specific times of day (local) being when the pressure change due to diurnal variation is at the mean pressure)
Any help or guidance is appreciated.

Anyone got an idea on how to plot values from only 4 specific times of day? (even though the values are gathered every 30s)?

Perhaps it would be better to create another influx-database and have Node-Red fill it with values from only the 4 specific times of day I need?

hmmmm, not sure
Cheers, Sean