CREATE TABLE table_1635 ("Period" TEXT, "% trains arriving within 5 mins of scheduled time  ( over three months ) " TEXT, "Change over same quarter the previous year" TEXT, "% trains arriving within 5 mins of scheduled time Moving Annual Average  ( MAA ) " TEXT, "Change over previous year as a whole" TEXT)

When was the percentage of trains arriving within 5 minutes of scheduled time 89.6%?
SELECT "Period" FROM table_1635 WHERE "% trains arriving within 5 mins of scheduled time Moving Annual Average (MAA)" = '89.6%'
SELECT "Period" FROM "table_1635" WHERE "% trains arriving within 5 mins of scheduled time Moving Annual Average (MAA)" = '89.6%'