Time formatting template. Unexpected 4 minutes being added

Configuration
1

I’m converting the time from one of my sensors from 24H to 12H format.

Here is my template:
{{ as_timestamp(strptime(states('sensor.ring_front_door_last_activity'), "%H:%M")) | timestamp_custom('%I:%M %p') }}

This is working (sort of)… If the sensor time is “13:45” the template result displays “01:49 PM”… it adds 4 minutes to the actual time.

So, I tested the following:
{{ as_timestamp(strptime("16:50", "%H:%M")) | timestamp_custom('%I:%M %p') }}
and got:
04:54 PM
Again… phantom 4 minutes

Then I tested:
{{ as_timestamp(now()) | timestamp_custom('%I:%M %p') }}
And got the correct result.

So, am I using strptime() incorrectly? Or is there another issue here?

2

I found that the workaround is to subtract the additional minutes in the code. Quantity of 50 = 1 min. So subtracting 200 reduces the added 4 min.:

{{ (as_timestamp(strptime(states('sensor.ring_front_door_last_activity'), '%H:%M')) -200) | timestamp_custom('%I:%M %p') }}