Hi, only one day for the submission for the particular challenge. I usually make the post for that day (for example - North American Friday) around 11:00 AM - those time change based on my schedule and all the participants have until 8:00 AM for their submissions from which I choose winning images. No need to worry if you miss that day since the challenge is ongoing and you can submit again next week. Hope that helps. I hope to see some of your entries soon. Tomas