Xiaomi announced Redmi Y1 and Redmi Y1 Lite along with MIUI 9 Global ROM on 2nd Nov in an event and released a schedule for MIUI 9 stable ROM roll out. As per the schedule, Redmi Y1, Redmi Y1 were kept in second batch of devices which were supposed to receive MIUI 9 update in mid November. Yesterday morning Xiaomi started rolling out a Stable Nightly update for Mi 5 and the same day in evening Stable Nightly update roll out began for Redmi Y1.
Nightly Stable ROMs are rolled out to random users, for more info on Nightly Stable builds refer to this post. The new update comes as MIUI 22.214.171.124.NDKMIEI and also brings October security patch to Redmi Y1.
Xiaomi is also asking for feedback from the users who have received this update, in case you have got update on your device you can submit your feedback here.
[Update 2: Xiaomi has announced that roll out of Global Stable MIUI 9 ROM for Redmi Y1 and Redmi Y1 Lite has been delayed and will be rolled out for all users in a couple of days]
[Update: Xiaomi has announced that Global Stable MIUI 9 ROM will be available for Redmi Y1 and Redmi Y1 Lite will roll out from tomorrow, November 16th.]"Xiaomi Redmi Y1 MIUI 9 Stable ROM now in testing [Update]",