Despite reviewing help datetime, searching Statalist, and reaching out to colleagues, I cannot solve this issue and kindly request any insights you may have. Thank you in advance.

Goal: Find the earliest date and time from three datetime variables for an observation.
Issue: Despite using double precision and clock function, the earliest time is milliseconds inconsistent with the earliest time.
Version: Stata 17.0 on Windows 10

Code excerpt

* format operative date
gen date_op_date = date(op_date,"DM20Y")
format %-tdNN/DD/CCYY date_op_date

* format operative time
gen double time_op_time = clock(op_inc_time,"hm")
format %tcHH:MM time_op_time

* combine operative date and time
gen double date_time_op = dhms(date_op_date,hh(time_op_time),mm(time_op_time ),ss(time_op_time))
format date_time_op %tcNN/DD/CCYY_HH:MM:SS

* keep earliest date/time
gen date_time_anchor = min(date_time_ed_arr, date_time_admit, date_time_op)
format date_time_anchor %tcNN/DD/CCYY_HH:MM:SS


Output excerpt w/example data (anchor should be the lowest/earliest)

date_time_ed_arr---------date_time_admit-----------date_time_op---------------date_time_anchor
03/01/2019 01:51:00-----03/01/2019 06:59:00-----03/01/2019 10:51:00------03/01/2019 01:51:42
03/01/2019 11:35:00-----03/01/2019 16:55:00-----03/01/2019 17:15:00------03/01/2019 11:34:58
03/01/2019 00:45:00-----03/01/2019 09:06:00-----03/01/2019 18:45:00------03/01/2019 00:43:58
03/01/2018 02:03:00-----03/01/2018 02:50:00------03/01/2018 12:38:00-----03/01/2018 02:03:54

Example generated by -dataex-
clear
input double(date_time_ed_arr date_time_admit date_time_op) float date_time_anchor
1867024260000 1867042740000 1867056660000 1.8670243e+12
1.8670593e+12 1.8670785e+12 1.8670797e+12 1.8670593e+12
1.8670203e+12 1867050360000 1.8670851e+12 1.8670202e+12
1.8354495e+12 . 1835538180000 1.8354495e+12
1835488980000 1.8354918e+12 1835527080000 1.835489e+12
end
format %tcNN/DD/CCYY_HH:MM:SS date_time_ed_arr
format %tcNN/DD/CCYY_HH:MM:SS date_time_admit
format %tcNN/DD/CCYY_HH:MM:SS date_time_op
format %tcNN/DD/CCYY_HH:MM:SS date_time_anchor