How do I show actual dates in a daily time series in R?

I've created a daily time series. Original data:

> head(platinum)
        Date Hong.Kong.8.30
1 2019-12-19            938
2 2019-12-18            929
3 2019-12-17            933
4 2019-12-16            931
5 2019-12-13            947
6 2019-12-12            943

I used the zoo package, and it still showed dates:

> plat2=read.zoo(platinum)
> tail(plat2,30)
2019-11-08 2019-11-11 2019-11-12 2019-11-13 2019-11-14 2019-11-15 
       913        894        880        876        878        885 
2019-11-18 2019-11-19 2019-11-20 2019-11-21 2019-11-22 2019-11-25 
       896        899        915        923        917        897 

After as.ts, however, the dates are stored as integers:

> as.ts(plat2)
Time Series:
Start = 8217 
End = 18249 
Frequency = 1 

And the plot is in intergers too: time series plot

I want the x axis to have intervals of a decade. Any help is appreciated.