diff --git a/.github/workflows/R-CMD-check-dev.yaml b/.github/workflows/R-CMD-check-dev.yaml
index cd73056..49b3433 100644
--- a/.github/workflows/R-CMD-check-dev.yaml
+++ b/.github/workflows/R-CMD-check-dev.yaml
@@ -18,7 +18,7 @@ jobs:
       fail-fast: false
       matrix:
         config:
-          - {os: windows-latest, r: 'release'}
+          # - {os: windows-latest, r: 'release'}
           - {os: ubuntu-latest,   r: 'oldrel-1'}
 
     env:
diff --git a/R/as_der.R b/R/as_der.R
index 89407c8..617cc15 100644
--- a/R/as_der.R
+++ b/R/as_der.R
@@ -29,7 +29,7 @@ as.der.pqcrypto_timestamp <- function (ts) {
   # dates in 2050 or later MUST be encoded as GeneralizedTime.
   # -- RFC 5280
 
-  dt <- as.POSIXlt(attr(ts, "unix_ts"), tz="UTC")
+  dt <- as.POSIXlt(attr(ts, "unix_ts"), tz="UTC", origin = "1970-01-01")
   if (dt$year <= 49 || dt$year >= 150) {
     # GeneralizedTime
     strdate <- strftime(dt, "%Y%m%d%H%M%SZ", tz="UTC")