I typically don't use daytime lights, but I always dress with a brightly colored shirt, usually neon green, yellow, or safety orange. I also have a bright yellow biking jacket for use during cooler weather which has reflective strips on it. But in anything less than sunny weather, such as dawn, dusk, or gloomy overcast I will put my headlight in strobe with maybe a blinking or twinkling rear light. Then in the dark I have full on headlight and taillight, but my helmet came with a small light on the back which I'll turn on blinking mode.
I suppose it would be safer to have lights on during the day, but I hate to run my batteries down. My sister has one of those really neat and really bright USB-rechargable taillights with numerous blinking patterns and which can be seen for something like 1/4 mile or more.