In Which I Outsmart Myself

Shift trading is a nice thing, quite a perk.
Such practice is how I made Balticon,
And shall make other trips this year. Shift work
Does have its benefits, but look upon
My error on this morning and beware!
Right now my workday really starts at nine,
But she who traded with me, who did share
A need to tweak a schedule. Unlike mine,
Her workday starts much earlier, I knew,
But last night I convinced myself that I
Should be there right at five. That's what I do!
Arriving, my surprised colleagues weren't shy.
"Six thirty's when you're needed," quoth they then.
I sighed and pedaled off, fooled once again.