public Date calculateNextTrigger(Calendar baseCalendar) {
        // All occurrences are done
        if (isLastOccurrence()) return null;

        // trigger: { in: 1, unit: 'hour' }
        // Catch wrong trigger units
        try {
            addInterval(baseCalendar, optionsTrigger.getUnit(), optionsTrigger.getIn());
            return baseCalendar.getTime();
        } catch (IllegalArgumentException exception) {
            Log.e(TAG, "Error calculating trigger, trigger unit is wrong: " + exception.getMessage());
            return null;
        }
    }
Calculates the next trigger.
@param baseCalendar The base calendar from where to calculate the next trigger.
src/android/trigger/TriggerHandlerIn.java