This isn't an issue for me anymore, as I'm taking a break from hospital work, and doing public health surveillance, but in the old days :chuckle we needed to call in by noon (I worked 3 to 11). Night shift by 1900 and days 0500. You could pretty much tell by the census if you needed to drag your butt in or not. Some days it would have taken bleeding from the eyes to call off, and others, well a snotty nose and body aches would suffice.