Many a time
Definition 1 of 1
Pro Tip 1/3Frequency Emphasis
Used to stress the frequency of an action or occurrence, more than 'often' would. 
She'd visited the old library many a time, soaking in its history.
Pro Tip 2/3Emotional Nostalgia
Can evoke a sense of nostalgia or romanticize past experiences. 
Many a time, we'd stroll along the beach, carefree and young.
Pro Tip 3/3Literary Flair
Often found in literature and storytelling to add an old-fashioned or poetic touch. 
Many a time have I hearkened to the song of the nightingale.