Switch to ISO 8601 while we're at it, but the important change here is to round
down to a value that tostring() can always handle.
--- a/src/init.lua
+++ b/src/init.lua
@@ -3166,7 +3166,7 @@ end
 
 -- Renders the fifth column in the table
 xplr.fn.builtin.fmt_general_table_row_cols_4 = function(m)
-  return tostring(os.date("%a %b %d %H:%M:%S %Y", m.last_modified / 1000000000))
+  return tostring(os.date("%Y-%m-%d %H:%M:%S", math.floor(m.last_modified / 1000000000)))
 end
 
 -- DEPRECATED: This function is just for compatibility.