Java Utililty Methods Date Start

Calendar cal = new GregorianCalendar();
cal.setTime(date);
cal.set(Calendar.HOUR, -12);
cal.set(Calendar.MINUTE, 0);
cal.set(Calendar.SECOND, 0);
date = cal.getTime();
return date;

Calendar cal = Calendar.getInstance();
cal.setTime(date);
int year = cal.get(Calendar.YEAR);
int month = cal.get(Calendar.MONTH) + 1;
int day = cal.get(Calendar.DAY_OF_MONTH);
Date start = getDate(year, month, day);
return start;

Calendar startOfDay = Calendar.getInstance();
startOfDay.setTime(day);
startOfDay.set(Calendar.HOUR_OF_DAY, 0);
startOfDay.set(Calendar.MINUTE, 0);
startOfDay.set(Calendar.SECOND, 0);
startOfDay.set(Calendar.MILLISECOND, 0);
return startOfDay.getTimeInMillis();

Calendar calendar = Calendar.getInstance();
calendar.setTime(day);
calendar.set(Calendar.HOUR_OF_DAY, 0);
calendar.set(Calendar.MINUTE, 0);
calendar.set(Calendar.SECOND, 0);
calendar.set(Calendar.MILLISECOND, 0);
return calendar.getTime();

java.util.Calendar cal = java.util.Calendar.getInstance();
cal.setTime(date);
cal.set(java.util.Calendar.DATE, 1);
return cal.getTime();

if (dt == null)
    return null;
GregorianCalendar gc = new GregorianCalendar();
gc.setTime(dt);
gc.set(Calendar.DAY_OF_MONTH, 1);
gc.set(Calendar.HOUR_OF_DAY, 0);
gc.set(Calendar.MINUTE, 0);
gc.set(Calendar.SECOND, 0);
...

Calendar c = Calendar.getInstance();
c.setTime(dt);
c.set(Calendar.DAY_OF_MONTH, 1);
return c.getTime();

if (dt == null)
    return null;
GregorianCalendar gc = new GregorianCalendar();
gc.setTime(dt);
int thisMonth = gc.get(Calendar.MONTH);
switch (thisMonth) {
case Calendar.JANUARY:
case Calendar.FEBRUARY:
...

if (serviceStartTime == null) {
    return null;
Calendar startTime = Calendar.getInstance();
startTime.setTime(serviceStartTime);
startTime.set(Calendar.MINUTE, 0);
startTime.set(Calendar.SECOND, 0);
startTime.set(Calendar.MILLISECOND, 0);
...

Calendar calendar = getCalendarByDate(date);
calendar.set(11, 0);
calendar.set(12, 0);
calendar.set(13, 0);
calendar.set(14, 0);
return calendar.getTime();