diff --git a/NEWS.md b/NEWS.md
index 2a00fd24..1165c962 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,8 @@
 # cli (development version)
 
+* New `{.duration}` and `{.time_ago}` inline styles to format durations
+  and relative times (@jjjermiah, #814).
+
 # cli 3.6.6
 
 * New `{.num}` and `{.bytes}` inline styles to format numbers
diff --git a/R/themes.R b/R/themes.R
index 26c94d18..71ada3a0 100644
--- a/R/themes.R
+++ b/R/themes.R
@@ -267,6 +267,15 @@ builtin_theme <- function(dark = getOption("cli.theme_dark", "auto")) {
     ),
     span.num = list(
       transform = function(x) format_num$pretty_num(as.numeric(x))
+    ),
+    span.duration = list(
+      transform = function(x) {
+        if (inherits(x, "difftime")) units(x) <- "secs"
+        format_time$pretty_sec(as.numeric(x))
+      }
+    ),
+    span.time_ago = list(
+      transform = function(x) format_time_ago$time_ago(as.POSIXct(x, origin = "1970-01-01"))
     )
   )
 }
diff --git a/tests/testthat/_snaps/inline-2.md b/tests/testthat/_snaps/inline-2.md
index 4ffce625..7004ff24 100644
--- a/tests/testthat/_snaps/inline-2.md
+++ b/tests/testthat/_snaps/inline-2.md
@@ -458,3 +458,46 @@
     Output
       [1] "--- 10 k, 20 k, 30 k, and 40 k ---"
 
+# .duration
+
+    Code
+      format_inline("--- {.duration 0.042} ---")
+    Output
+      [1] "--- 42ms ---"
+    Code
+      format_inline("--- {.duration 90} ---")
+    Output
+      [1] "--- 1m 30s ---"
+    Code
+      format_inline("--- {.duration 3661} ---")
+    Output
+      [1] "--- 1h 1m 1s ---"
+    Code
+      dt_mins <- as.difftime(1.5, units = "mins")
+      format_inline("{.duration {dt_mins}}")
+    Output
+      [1] "1m 30s"
+    Code
+      dt_days <- as.difftime(30, units = "days")
+      format_inline("{.duration {dt_days}}")
+    Output
+      [1] "30d"
+
+# .time_ago
+
+    Code
+      t <- as.numeric(Sys.time() - 120)
+      format_inline("{.time_ago {t}}")
+    Output
+      [1] "2 minutes ago"
+    Code
+      t <- Sys.time() - 120
+      format_inline("{.time_ago {t}}")
+    Output
+      [1] "2 minutes ago"
+    Code
+      t <- as.POSIXlt(Sys.time() - 120)
+      format_inline("{.time_ago {t}}")
+    Output
+      [1] "2 minutes ago"
+
diff --git a/tests/testthat/test-inline-2.R b/tests/testthat/test-inline-2.R
index 0b9da477..67436653 100644
--- a/tests/testthat/test-inline-2.R
+++ b/tests/testthat/test-inline-2.R
@@ -212,3 +212,35 @@ test_that(".num", {
     format_inline("--- {.num {1:4 * 10000}} ---")
   })
 })
+
+test_that(".duration", {
+  expect_snapshot({
+    # numeric seconds
+    format_inline("--- {.duration 0.042} ---")
+    format_inline("--- {.duration 90} ---")
+    format_inline("--- {.duration 3661} ---")
+
+    # difftime: units normalised before formatting (not treated as raw seconds)
+    dt_mins <- as.difftime(1.5, units = "mins")
+    format_inline("{.duration {dt_mins}}")
+
+    dt_days <- as.difftime(30, units = "days")
+    format_inline("{.duration {dt_days}}")
+  })
+})
+
+test_that(".time_ago", {
+  expect_snapshot({
+    # numeric unix timestamp
+    t <- as.numeric(Sys.time() - 120)
+    format_inline("{.time_ago {t}}")
+
+    # POSIXct
+    t <- Sys.time() - 120
+    format_inline("{.time_ago {t}}")
+
+    # POSIXlt
+    t <- as.POSIXlt(Sys.time() - 120)
+    format_inline("{.time_ago {t}}")
+  })
+})