With <setdcalarmtime> it is possible to set a — absolute (independent from dive time) — time when the dive computer shall give an alarm.
(see also <setdcdata>)
<setdcalarmtime>
    <time>
        <hour>14</hour>
        <minute>37</minute>
    </time>
    <dcalarm>
        <!-- duration 10 seconds -->
        <period>10.0</period>
        <alarmtype>1</alarmtype>
    </dcalarm>
</setdcalarmtime>