Python ValueError:视图限制最小值-36834.700000？

我正在根据数据文件绘制1998年和2017年的最高和最低温度。2017年部分缺失了几天，因此只有345天，1998年为365天。以下是我所拥有的：

napa=pd.read_csv('MET 51 Final data selection.csv')

maxtemp=napa['TMAX']
mintemp=napa['TMIN']
days=[i for i in range(365)]
days2=[i for i in range(345)]
plot(days,maxtemp[7273:7638],'r--',label='Maximum Temperatures (1998)')
plot(days,mintemp[7273:7638],'b--',label='Minimum Temperatures (1998)')
plot(days2,maxtemp[14172:14517],color='crimson',label='Maximum Temperatures (2017)')
plot(days2,mintemp[14172:14517],color='deepskyblue',label='Minimum Temperatures (2017)')
xlabel('Time (Days)')
ylabel('Temperature (F)')
title('Napa State Hospital Maximum & Minimum Temperatures 1998 VS 2017')
legend()
show()

然而，我不断得到这样的错误：

ValueError: view limit minimum -36834.700000000004 is less than 1 and is an invalid Matplotlib date value. This often happens if you pass a non-datetime value to an axis that has datetime units

你知道怎么了吗