You can use the following syntax to convert a string to a datetime in R:

as.POSIXct(string_name, format="%Y-%m-%d %H:%M:%S", tz="UTC")

The following examples show how to use this syntax in practice:

Example 1: Convert One String to Datetime

The following code shows how to convert a single string in R to a datetime format:

#define string variable
string_x <- "2020-01-01 14:45:18"

#convert string variable to datetime variable
datetime_x <- as.POSIXct(string_x, format="%Y-%m-%d %H:%M:%S", tz="UTC")

#view new datetime variable
datetime_x

[1] "2020-01-01 14:45:18 UTC"

#view class of datetime variable 
class(datetime_x)

[1] "POSIXct" "POSIXt" 

Example 2: Convert Column of Strings to Datetime

Suppose we have the following data frame with a column that contains a string of datetimes:

#define data frame
df <- data.frame(day=c("2020-01-01 14:45:18", "2020-02-01 14:00:11",
                            "2020-03-01 12:40:10", "2020-04-01 11:00:00"),
                 sales=c(13, 18, 22, 19))

#view data frame
df

                  day sales
1 2020-01-01 14:45:18    13
2 2020-02-01 14:00:11    18
3 2020-03-01 12:40:10    22
4 2020-04-01 11:00:00    19

We can convert this column from strings to datetimes using the following syntax:

#convert column of strings to datetime
df$day <- as.POSIXct(df$day, format="%Y-%m-%d %H:%M:%S", tz="UTC")

#view class of 'day' column
class(df$day)

[1] "POSIXct" "POSIXt" 

Note that in these examples we used a specific datetime format. Refer to for a complete documentation of the potential datetime formats you can use.