Set ZBX_MIN_PERIOD in defines.inc.php to 5 seconds. Play with custom time period values back and forth. For example, set "From": 2017-12-31 23:59:59
And then change "To" second by second:

• 2018-01-01 00:00:04 - Works fine.
• 2018-01-01 00:00:03 - Nothing visually changed, but CPU usage has gone up to 12%.
• 2018-01-01 00:00:02 - Get error: "Minimum time period to display is 0.083333333333333 minutes."
• 2018-01-01 00:00:03 - Error did not disappear, but CPU usage has gone up to 24%.
• 2018-01-01 00:00:04 - Error is gone.
• 2018-01-01 00:00:03 - Nothing visually changed, but CPU usage has gone up to 36%.

Another way.
Set ZBX_MIN_PERIOD in defines.inc.php to 1 seconds. Play with custom time period values. For example, set "From": 2017-12-31 23:59:59
And then change "To" second by second:
2018-01-01 00:00:00 - CPU usage 12%
2018-01-01 00:00:01 - CPU usage 25%
2018-01-01 00:00:02 - CPU usage 35%
2018-01-01 00:00:03 - CPU usage 43%
2018-01-01 00:00:04 - CPU usage still around 41-45%, but seems to stop going higher after this.

If ZBX_MIN_PERIOD is set to 6 seconds, seems to work fine, but with 5 or less seconds, script goes into infinite loop.