Date boundary functions

dateBoundaries.js

/* Useful date functions if you're building a calendar */

var getStartOfCurrentDay = function(date) {
  return new Date(date.getFullYear(), date.getMonth(), date.getDate());
};

var getStartOfNextDay = function(date) {
  return new Date(date.getFullYear(), date.getMonth(), date.getDate() + 1);
};

var getEndOfPreviousDay = function(date) {
  return new Date(getStartOfCurrentDay(date).getTime() - 1);
};

var getEndOfCurrentDay = function(date) {
  return getEndOfPreviousDay(getStartOfNextDay(date));
};

var getStartOfCurrentWeek = function(date, firstWeekday) {
  firstWeekday = firstWeekday || 0;
  var offset = ((7 + date.getDay() - firstWeekday) % 7) * 86400000;
  return getStartOfCurrentDay(new Date(date.getTime() - offset));
};

var getStartOfNextWeek = function(date) {
  return new Date(getStartOfCurrentWeek(date).getTime() + 604800000);
};

var getEndOfPreviousWeek = function(date) {
  return new Date(getStartOfCurrentWeek(date).getTime() - 1);
};

var getEndOfCurrentWeek = function(date) {
  return getEndOfPreviousWeek(getStartOfNextWeek(date));
};

var getStartOfCurrentMonth = function(date) {
  return new Date(date.getFullYear(), date.getMonth(), 1);
};

var getStartOfNextMonth = function(date) {
  return new Date(date.getFullYear(), date.getMonth() + 1, 1);
};

var getEndOfPreviousMonth = function(date) {
  return new Date(getStartOfCurrentMonth(date).getTime() - 1);
};

var getEndOfCurrentMonth = function(date) {
  return getEndOfPreviousMonth(getStartOfNextMonth(date));
};

var getStartOfCurrentYear = function(date) {
  return new Date(date.getFullYear(), 0, 1);
};

var getStartOfNextYear = function(date) {
  return new Date(date.getFullYear() + 1, 0, 1);
};

var getEndOfPreviousYear = function(date) {
  return new Date(getStartOfCurrentYear(date).getTime() - 1);
};

var getEndOfCurrentYear = function(date) {
  return getEndOfPreviousMonth(getStartOfNextYear(date));
};