[D] How do you handle the lack of data in a research project for testing?

The thing I have is randomly sampling days from the year however this runs into flaws of the day just not being optimal. Other research papers in related work has two years one for training and another for testing. I only have one year and asked the professor for another year of data and he said it isn’t available with no explanation behind it. I tried searching online for the data since it’s supposedly public data but can’t find it. …

data flaws machinelearning project research sampling testing training work