--- a/util/datetime.lua	Sun Aug 14 16:51:10 2022 +0200
+++ b/util/datetime.lua	Sun Aug 14 16:57:31 2022 +0200
@@ -12,31 +12,42 @@
 local os_date = os.date;
 local os_time = os.time;
 local os_difftime = os.difftime;
+local floor = math.floor;
 local tonumber = tonumber;
 
 local _ENV = nil;
 -- luacheck: std none
 
 local function date(t)
-	return os_date("!%Y-%m-%d", t);
+	return os_date("!%Y-%m-%d", t and floor(t) or nil);
 end
 
 local function datetime(t)
-	return os_date("!%Y-%m-%dT%H:%M:%SZ", t);
+	if t == nil or t % 1 == 0 then
+		return os_date("!%Y-%m-%dT%H:%M:%SZ", t);
+	end
+	local m = t % 1;
+	local s = floor(t);
+	return os_date("!%Y-%m-%dT%H:%M:%S.%%06dZ", s):format(floor(m * 1000000));
 end
 
 local function time(t)
-	return os_date("!%H:%M:%S", t);
+	if t == nil or t % 1 == 0 then
+		return os_date("!%H:%M:%S", t);
+	end
+	local m = t % 1;
+	local s = floor(t);
+	return os_date("!%H:%M:%S.%%06d", s):format(floor(m * 1000000));
 end
 
 local function legacy(t)
-	return os_date("!%Y%m%dT%H:%M:%S", t);
+	return os_date("!%Y%m%dT%H:%M:%S", t and floor(t) or nil);
 end
 
 local function parse(s)
 	if s then
 		local year, month, day, hour, min, sec, tzd;
-		year, month, day, hour, min, sec, tzd = s:match("^(%d%d%d%d)%-?(%d%d)%-?(%d%d)T(%d%d):(%d%d):(%d%d)%.?%d*([Z+%-]?.*)$");
+		year, month, day, hour, min, sec, tzd = s:match("^(%d%d%d%d)%-?(%d%d)%-?(%d%d)T(%d%d):(%d%d):(%d%d%.?%d*)([Z+%-]?.*)$");
 		if year then
 			local now = os_time();
 			local time_offset = os_difftime(os_time(os_date("*t", now)), os_time(os_date("!*t", now))); -- to deal with local timezone
@@ -49,8 +60,9 @@
 				tzd_offset = h * 60 * 60 + m * 60;
 				if sign == "-" then tzd_offset = -tzd_offset; end
 			end
-			sec = (sec + time_offset) - tzd_offset;
-			return os_time({year=year, month=month, day=day, hour=hour, min=min, sec=sec, isdst=false});
+			local prec = sec%1;
+			sec = floor(sec + time_offset) - tzd_offset;
+			return os_time({year=year, month=month, day=day, hour=hour, min=min, sec=sec, isdst=false})+prec;
 		end
 	end
 end