These settings are available in system.settings and are autogenerated from the ClickHouse snapshot.
formatdatetime_f_prints_scale_number_of_digits
Formatter ‘%f’ in function ‘formatDateTime’ prints only the scale amount of digits for a DateTime64 instead of fixed 6 digits.
formatdatetime_f_prints_single_zero
Formatter ‘%f’ in function ‘formatDateTime’ prints a single zero instead of six zeros if the formatted value has no fractional seconds.