Create a single time series plot of multiple devices
You can create overlapping plots by looping over your dataset and plotting onto the same axes:
ax, fig = plt.subplots()
n = 30 # number of device
for i in (number+1 for number in range(n)):
    ax.plot(data[i], label='device_0' + i)

plt.show()

It might be best to first put your data into a pandas Dataframe.
In regard to the X-axis, you will need to convert the seconds to datetime, by adding an estimate of the starting date to each value in the dataset.