Possible Clues:

• Browning's bedtime?
• Dark period of poetry
• Dusk, to John Donne
• Poet's early night
• When night comes o'er the land
• Poetic form of even
• Even a car might not be on an even keel over this
• Poetic gloaming
• 'Is it ___ so? Then I defy you, stars!': Romeo
• Contraction before 'now'