A Korean media said that the Galaxy S8 will be globally launched on April 21, 2017.

Samsung Electronics originally planned to launch Galaxy S8 worldwide on the 21st of April and in Korea, a week earlier. Its initial plan was to commence pre-sales on the 6th of April and launch
Galaxy S8 in South Korea on the 14th of April. Samsung is yet to make decision on pre-sale date though the flagship release date has already been fixed for April 21

However, due to the size of supplies and for stable supplies to carriers, it decided to alter its plan by having Galaxy S8 launched internationally and domestically on the same day.

“Release date of Galaxy S8 in South Korea has changed from the 14th of April to the 21st of April due to reasons such as size of supplies and others.” said a high-profile official for a carrier.

Three Korean network providers are said to have been in discussions with Samsung regarding the
pre-order date of the Galaxy S8, but Samsung is alleged to be playing waiting games in order to monitor the feedback from LG G6 market.

LG G6 will go official on February 26 but won't be market for buying until March 10. Nonetheless, customers will be allowed to pre-order the LG flagship between March 2 and March 9.

Since LG G6 will go live almost a month before Galaxy S8, a rep for a carrier was quoted saying, “dynamics of markets will heighten due to competitions” between these two companies.

http://www.tellforceblog.com/2017/02/samsung-galaxy-s8-to-be-launched-on.html