You can do this by customizing the plugin.
You’ll want to find timepicker.js in /wp-content/plugins/acf-field-date-time-picker/js/timepicker.js
And change line 21:
, yearRange: "-100:+100"
to your preferred range, for example:
, yearRange: "-500:+100"
This gives you a dropdown that, by default, goes back 500 years and forth 100, from the current year.
Or you can hardcode a specific range like this, to fit your specific needs:
, yearRange: "1500:1699"
Of course these will be overridden if the plugin gets updated, but it’s a quick fix to your current issue.
The whole code-block looks like this by default:
input.addClass('active').attr("placeholder", (is_timeonly) ? time_format : date_format + ' ' + time_format).datetimepicker({
changeYear: true
, yearRange: "-100:+100"
, changeMonth: true
, timeOnly: is_timeonly
, timeFormat: time_format
, dateFormat: date_format
, showWeek: (input.attr('data-show_week_number') != "true") ? 0 : 1
, ampm: has_ampm
, controlType: input.attr('data-picker')
, timeOnlyTitle: input.attr('title')
, monthNames: timepicker_objectL10n.monthNames
, monthNamesShort: timepicker_objectL10n.monthNamesShort
, dayNames: timepicker_objectL10n.dayNames
, dayNamesShort: timepicker_objectL10n.dayNamesShort
, dayNamesMin: timepicker_objectL10n.dayNamesMin
, firstDay: timepicker_objectL10n.firstDay
});