Last month, Microsoft said that it would no longer be supporting the original version of Windows 10 beginning on March 26. Version 1507 is now slated to lose servicing support in May.
Last month, Microsoft announced that the Windows 10 Anniversary Update (version 1607) would be coming to the Volume Licensing Service Center (VLSC) on January 26. Since only the two latest versions of Windows 10 are to be supported at once, a 60-day grace period would begin for the original version of the OS, 1507, marking an end-of-life date for March 26.
Microsoft has since updated the TechNet article , saying that version 1507 will no longer be serviced in May, rather than March.