sunday 前唔需加on?

何解The 35th Hong Kong International Film Festival (HKIFF) opens Sunday with screenings of two films, the romantic comedy “Don’t Go Breaking My Heart” and “Quattro Hong Kong 2.”opens 後唔需加on?

在wall street journal 看到的,,,,editor 當然沒有看漏.雖然在日期date,前加on是常规, 但on並非必須的,正如opens後就可不用了.

其他例子:
Sunday:
Hanover Major League opens Sunday (http://www.jamaicaobserver.com/westernnews/Hanover-Major-League-opens-Sunday_8532947)Extensive new exhibit opens Sunday at Elgin historical society site(http://couriernews.suntimes.com/lifestyles/4222750-423/extensive-new-exhibit-opens-sunday-at-elgin-historical-society-site.html) Sunrise Park Resort will be open Sunday morning.(http://www.myfoxphoenix.com/dpp/entertainment/sunrise-ski-resort-opens-sunday-12252010)Voting closes Sunday! (http://lessoninpride.blogspot.com/2011/03/etihad-coming-home-competition-voting.html)Other days/dates:
The annual Attic Productions youth show opens March 24 and runs the 24th through 26th and then again March 31-April 2.(http://blogs.roanoke.com/botetourtview/2011/03/photos-attic-productions-youth-show-opens-march-24/)Community awareness seminar starts Tuesday, March 22 (http://www.wmicentral.com/calendar/community-awareness-seminar-starts-tuesday-march/event_7f7af70e-4f42-11e0-a237-001cc4c03286.html)

2011-03-22 17:00:48 補充：
henry ,
When on is not used as in "'The 35th Hong Kong International Film Festival (HKIFF) opens Sunday", it actually means "The 35th Hong Kong International Film Festival (HKIFF) opens this/next Sunday" with this/next omitted. (Jenkin mentioned this in his answer,)

2011-03-22 17:14:28 補充：
In that sense, sentences with this/next 'day of the week' can have the preposition 'on' omitted.
For a date (dd/mm/yy), some other verbs that do not require 'on' before the date are:
begin, start, commence, stop, finish, terminate.
Hope these are useful.

COOL!!!!
thanks eica!!!

I don't think you can omit the word 'on'. Maybe you can also use 'next'.

The 35th Hong Kong International Film Festival (HKIFF) opens ON Sunday - 27/3.


The 35th Hong Kong International Film Festival (HKIFF) BEGINS ON Sunday - 27/3

要on Sunday，
如果可以更清楚，例如寫this Sunday 還是next Sunday便更好。